## Online Education MCQ Questions for Class 10 Science Chapter 9 Heredity and Evolution with Answers

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## Online Education for Heredity and Evolution Class 10 MCQs Questions with Answers

Heredity And Evolution Class 10 MCQ Question 1.
In peas, a pure tall plant (TT) is crossed with a pure short plant (tt). The ratio of pure tall plants to pure short plants in F2 generation will be:
(a) 1: 3
(b) 3:1
(c) 1:1
(d) 2:1
(c) 1:1

Explanation: The genotype ratio of F2 generation is: TT: Tt: tt = 1: 2: 1. Therefore, the ratio of TT and tt plants of F2 generation will be the same.

Heredity Class 10 MCQ Question 2.
Two pink-colored flowers on crossing resulted in 1 red, 2 pink, and 1 white flower progeny. The nature of the cross will be:
(a) Double fertilization
(b) Self-pollination
(c) Cross-fertilization
(d) No fertilization
(c) Cross-fertilization

Explanation: The nature of the cross will be cross fertilization, which is the transfer of pollen from one plant to the stigma of flower; borne on a different plant of the same species.

Related Theory:

• Self-pollination: Transfer of pollen grains from the anther to the stigma of the same flower of the same plant.
• Cross-pollination: Transfer of pollen grains from the anther of one flower to the stigma of another flower.
• Double fertilization: This process occurs when one male nucleus fertilizes (fuses) with the egg cell to form a zygote cell and the other male nucleus fuses (fertilizes) with two polar nuclei to cause triple fusion. These two types of fertilization take place at the same time in the ovule of the plant.

Heredity And Evolution MCQ Question 3.
In human males, all the chromosomes are paired perfectly except one. These unpaired chromosomes are:
(I) Large chromosome
(II) Small chromosome
(III) Y chromosome
(IV) X chromosome
(a) (I) and (II)
(b) (III) and (II)
(c) (III) and (IV)
(d) (II) and (IV)

Class 10 Heredity And Evolution MCQ Question 4.
Which of the following statement is incorrect?
(a) For every hormone there is a gene.
(b) For every protein there is a gene.
(c) For production of every enzyme there is a gene.
(d) For every molecule of fat there is a gene.
(d) For every molecule of fat there is a gene. Explanation: A section of DNA that provides information for one protein is called the gene for that protein. Hormones and enzymes are proteins, and the formation of any particular protein is controlled by a particular gene. Fat biosynthesis occurs through metabolic reaction. They are not related to genes.

MCQ On Heredity And Evolution Question 5.
Which one is a possible progeny in F2 generation of purebred tall plant with round seed and dwarf plant with wrinkled seeds?
(a) Tall plant with round seeds
(b) Tall plant with wrinkled seeds
(c) Dwarf plant with round seed
(d) All of the above

Heredity And Evolution MCQ Questions Question 6.
If a round, green-seeded pea plant (RR yy) is crossed with wrinkled, yellow seeded pea plant, (rr YY), the seeds production in the F1 generation are:
(a) Round and yellow
(b) Round and green
(c) Wrinkled and green
(d) Wrinkled and yellow
(a) Round and yellow

Explanation: The cross between RR yy and rr YY seeds will obtain RrYy offspring which will exhibit round and yellow phenotype, as these traits are the dominant ones.

MCQ Questions On Heredity And Evolution Class 10 Question 7.
A zygote which has an X chromosome inherited from the father will develop into a:
(a) Boy
(b) Girl
(c) X chromosome does not determine the sex of a child
(d) Either boy or girl
(b) Girl

Explanation: Humans follow XX- XY mechanism of sex determination i.e., women are XX while men are XY. All children will inherit an X chromosome from their mother regardless of whether they are boys or girls. Thus, the sex of the children will be determined by what they inherit from their father. A child who inherits an X chromosome from her father will be a girl and the one who inherits a Y chromosome from him will be a boy.

Heredity MCQ Class 10 Question 8.
Select the incorrect statement:
(a) The frequency of certain genes in a population change over several generations resulting in evolution.
(b) The reduction in the weight of an organism due to starvation is genetically controlled.
(c) Low weight parents can have heavy weight progeny.
(d) Traits which are not inherited over generations do not cause evolution.

MCQ Questions For Class 10 Science Chapter 9 Question 9.
Select the correct statement:
(a) The tendril of a pea plant and the phylloclade of Opuntia are homologous.
(b) The tendril of a pea plant and the phylloclade of Opuntia are analogous.
(c) The wings of birds and the limbs of lizards are analogous.
(d) The wings of bird and the wings of bats are homologous.

MCQs On Heredity And Evolution Class 10 Question 10.
If the fossil of an organism is found in the deeper layers of earth, then we can predict that:
(a) The extinction of the organism occurred recently.
(b) The extinction of the organism occurred thousands of years ago.
(c) The fossil position in the layers of Earth is not related to its time of extinction.
(d) The time of extinction cannot be deter¬mined.
(b) The extinction of the organism occurred thousands of years ago.

Explanation: If we dig into the earth and start finding fossils, the fossils we find closer to the surface are more recent than the fossils we find in deeper layers.

Related Theory
Depth of each stratum signifies the relative age of fossils present in it. The deeper the stratum, the older the rock and the fossils present in it

Class 10 Science Chapter 9 MCQ Question 11.
A trait in an organism is influenced by:
(a) Paternal DNA only
(b) Maternal DNA only
(c) Both maternal and paternal DNA
(d) Neither paternal nor maternal DNA
(c) Both maternal and paternal DNA

Explanation: DNA is contributed to an offspring by both the parents; hence, traits are influenced by both maternal and paternal DNA. During sexual reproduction, both mother and father pass their genes to their children, thus determining their traits; or characteristic features.

MCQ Of Heredity And Evolution Question 12.
New species may be formed if:
(I) DNA undergoes significant changes in germ cells.
(II) The chromosome number changes in the gamete.
(III) There is no change in the genetic material.
(IV) Mating does not take place.
(a) (I) and (II)
(b) (I) and (III)
(c) (II), (III) and (IV)
(d) (I), (II) and (III)

MCQ On Heredity And Evolution Class 10 Question 13.
which of the following statements is not true with respect to variation?
(a) All variations in a species have equal chances of survival.
(b) Change in genetic composition results in variation.
(c) Selection of variants by environmental factors forms the basis of evolutionary processes.
(d) Variation is minimum in asexual reproduction.

Heredity And Evolution Class 10 MCQ With Answers Question 14.
According to the evolutionary theory, for¬mation of a new species is generally due to:
(a) Sudden creation by nature.
(b) Accumulation of variations over several generations.
(c) Clones formed during asexual reproduction.
(d) Movement of individuals from one habitat to another.

Heredity And Evolution Class 10 MCQ Learn Cbse Question 15.
The theory of the evolution of species by natural selection was given by:
(a) Mendel
(b) Darwin
(c) Morgan
(d) Lamarck

Question 16.
Some dinosaurs had feathers although they could not fly but birds have feathers that help them to fly. In the context of evolution this means that:
(a) Reptiles have evolved from birds.
(b) There is no evolutionary connection between reptiles and birds.
(c) Feathers are homologous structures in both the organisms.
(d) Birds have evolved from reptiles.

Question 17.
Select a set of homologous organs from the following:
(a) Wings of a bat and wings of a butterfly
(b) Wings of a pigeon and wings of a bat
(c) Wings of a butterfly and wings of a pigeon
(d) Forelimbs of a duck, forelimbs of a cow and forelimbs of a lizard
(d) Forelimbs of a duck, forelimbs of a cow and forelimbs of a lizard

Explanation: Wings of a bat and wings of a butterfly (A), Wings of a pigeon and wings of a bat (B) and Wings of a butterfly and wings of a pigeon (C) are analogous organs as they all use wings for flying but the wings have different structures.

Bat wings consist of flaps of skin stretched between the bones of the fingers and arm, wings of pigeon consist of feathers extending all along the arm whereas butterfly wings are covered in scales.

On the other hand, Forelimbs of a duck, forelimbs of a cow and forelimbs of a lizard are homologous organs as they all have similar structures which have been modified to perform different functions.

Question 18.
Select the correct statements regarding monohybrid cross between a pure tall pea plant and pure short pea plant performed by Mendel:
(I) All plants of the F1 generation were tall.
(II) The tall plants in the F1 generation were exactly the same as the tall plants of the parent generation
(III) One-quarter of the F2 progeny of the F1 tall plants were short.
(IV) Both the tallness and shortness traits were inherited in the F1 plants
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (II) and (III)
(d) (I), (III) and (IV)
(d) (I), (III) and (IV)

Explanation: When a pure tall pea plant is crossed with a pure short plant, it was observed that all plants of the F1 generation were tall. But the tall plants in the F1 generation were not exactly the same as the tall plants of the parent generation. The genotype of the pure tall plant is TT, whereas the genotype of the tall plant in the F1 generation was Tt. The ratio of the tall and short plants in the F2 generation was 3:1. As 25 % of the pea plants in the F2 generation were tall, it means that both the shortness (t) and tallness (T) trait were inherited in the FI plants.

Question 19.
Which of the following are acquired traits?
(I) Attached or free earlobe
(II) Muscular body of a wrestler
(III) Body weight of starving animals
(IV) Brown and curly hair
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)

Question 20.
Consider the plants the pitcher plant, venus fly trap, poinsettia and cactus.
Select the row containing incorrect information regarding the leaves of these plants in terms of evolutionary relationships.

 (a) Leaves of these plants are homol­ogous organs The leaves are structurally simi­lar but modified to perform differ­ent functions (b) Leaves of these plants are analo­gous organs The leaves are structurally dis­similar but per­form similar func­tions (c) Leaves of these plants are vestig­ial organs Leaves are ho­mologous    to similar leaves in other plants (d) Leaves of these plants are neither homologous nor analogous The leaves have no structural or functional simi­larity

Question 21.
Study the organs and evolutionary relationship mentioned alongside. Select the row containing incorrect information.

 Organs Relationship Evolutionary (a) limbs of human being and frog Homologous organs (b) wings of bird and bat Analogous organs (c) Thorns and spines in plants Analogous organs (d) Tendril of pea plant and grape plant Homologous organs

(d) Organs: Tendril of pea plant and grape plant; Evolutionary Relationship: Homologous organs

Explanation: Thorn is modification of stem and spine is modification of leaf. Tendrils in plant show similar function but they are different in origin. Pea plant has Leaf tendril whears. Grape plant has Stem tendril

Question 22.
which of the statements regarding evolution is correct?
(a) One species is always eliminated in order to give rise to a new species.
(b) The newly formed species are better than the old species.
(c) Evolution is the generation of diversity and the shaping of the diversity by environmental selection.
(d) More and more complex body designs have emerged over time as the older designs are ineffcient.

Question 23.
which of the following cannot be an outcome of Mendel’s Experiment on crossing a tall pea plant with a short pea plant?
(a) 3 tall 1 short plant
(b) 4 tall plants and 1 medium height plant.
(c) 24 tall and 8 short plants
(d) 8 tall and 0 short plants

Question 24.
Which of the following have a perfect pair of sex chromosomes?
(a) Only Girls
(b) Only Boys
(c) Both girls and boys
(d) It depends on many other factors
(a) Only Girls

Explanation: Girls have a perfect paired 23rd chromosome, which is XX, whereas boys have a mismatched 23rd pair of chromosomes, which is XY.

Question 25.
Select the incorrect option.
Genetic drift is:
(a) A mechanism of evolution in which allele frequencies of a population remain constant over generations.
(b) It occurs in all populations of non-infinite size, but its effects are strongest in small populations.
(c) It may result in the loss of some alleles.
(d) It can have major effects when a population is sharply reduced in size by a natural disaster.

Question 26.
Select the group which shares the maximum number of common characters:
(a) Two individuals of a species
(b) Two species of a genus
(c) Two genera of a family
(d) Two genera of two families

Question 27.
Select the statements that describe the characteristics of genes:
(I) Genes are specific sequence of bases in a DNA molecule.
(II) A gene does not code for proteins.
(III) In individuals of a given species, a specific gene is located on a particular chromosome.
(IV) Each chromosome has only one gene.
(a) (I) and (II)
(b) (I) and (III)
(c) (I) and (IV)
(d) (III) and (IV)
(b) (I) and (III)

Explanation: Genes are units of heredity and are responsible for inheritance. Genes control the expression of a trait or a character in an organism. Genes are located on the chromosomes, which is present inside the nucleus of the cell in the crytoplasm.

Question 28.
The number of pair(s) of sex chromosomes in the zygote of humans is:
(a) One
(b) Two
(c) Three
(d) Four

### Assertion Reasoning questions Class 10 Science Chapter 9

For the following questions, two statements are given: one Labeled Assertion (A) and the other Labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 29.
Assertion (A): The wing of an insect and wing of a bird are analogous organs
Reason (R): The organs which are quite different in fundamental structure and origin but perform the same function in different species are called analogous organs

Question 30.
Assertion (A): The sex of a child in human beings will be determined by the type of chromosome he/ she inherits from the father.
Reason (R): A child who inherits ‘X‘ chromosome from his father would be a girl (XX), while a child who inherits a ‘Y‘ chromosome from the father would be a boy (XY).
(a) Both (A) and (R) are true and (R) is correct explanation of the (A).

Explanation: Human beings have 23 pairs of chromosomes. Out of which one pair is sex chromosomes and 22 pairs are autosomes. In men, sex chromosome pair is mismatched pair ‘XY‘, ‘X‘ is normal sized and Y is shorter than ‘X‘ chromosomes. Human females have ‘XX chromosomes. Males produce two types of sperms whereas females produce only one ovum having ‘X’ chromosomes. A child who inherits the ‘X’ chromosome from a father would be a girl ‘(XX)’.

While a child who inherits a Y chromosome from the father would be a boy (XY).

Question 31.
Assertion: A geneticist crossed a pea plant having violet flowers with a peaplant with white flowers, he got all violet flowers in first generation.
Reason: White colour gene is not passed on to next generation.

Question 32.
Assertion (A): New combination of traits are observed in F2 offspring when tall plants with round seeds are crossed with short plants with wrinkled seeds.
Reason (R): Tallness and round seed are both dominant traits.

(Competency Based Questions (CBQs))

Question 1.
Lokesh was very fond of dogs. So, one day his friend called him to show a white dog and a black dog which he had recently got from his friend. Lokesh was wondering as to how different dogs have different colours!

Dogs having black coat colour when crossed with dogs having same colour, produced 200 offsprings. Out of this 150 were black and 50 were white. The genotype of dogs is:
(a) BB and bb (B: Black; b: white)
(b) Bb and bb (B: Black; b: white)
(c) Bb and Bb (B: Black; b: white)
(d) BB and Bb (B: Black; b: white)
(a) BB and bb (B: Black; b: white)

Explanation: As the ratio of black: white dogs = 150 : 50 = 3 :1, black coat colour is dominant over white. Further, both black and white dogs are homozygous (BB and bb).

Question 2.
A giant 70 million year old fossil of a fish that lived amongst dinosaurs has been discovered in Argentine Patagonia, a team of researchers said on Monday.Argentine paleontologists “found the remains of a predator fish that was more than six meters long,” the researchers said in a statement.The discovery was published in the scientific journal Alcheringa: An Australasian Journal of Palaeontology.The fish “swam in the Patagonian seas at the end of the Cretaceous Period, when the temperature there was much more temperate than now,” the statement said.

Mention any two methods of estimating life of a fossil.
The two methods of estimating the life of a fossil are:
(1) By digging the earth and start finding fossils. The fossils found closer to the surface are more recent as compared to the fossils found in deeper layers.
(2) By detecting the ratios of different isotopes of a radioactive element in the fossil material, such as Carbon-14.

Question 3.
Inheritance from the previous generation provides both a common basic body design, and subtle changes in it, for the next generation. The original organism at the top will give rise to two individuals, similar in body design, but with subtle differences. Each of them, in turn, will give rise to two individuals in the next generation. Each of the four individuals in the bottom row will be different from each other. While some of these differences will be unique, others will be inherited from their respective parents, who were different from each other. Selection of variants by environmental factors forms the basis for evolutionary processes.
(A) If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Trait B is likely to have arisen earlier because in asexual reproduction traits are carried from parents to offspring with least variations so since trait B has higher percentage it is likely to have arisen earlier.

(B) How does the creation of variations in a species promote survival?
The Y chromosome in the zygote

Explanation: A child who inherits an X chromo¬some from her father will be a girl and the one who inherits a Y chromosome from him will be a boy. Thus the maleness of a child is determined by the presence of the Y chromosome in the zygote inherited from the father.

(C) Give any one factor that could lead to the rise of a new species?
The factors could lead to the rise of a new species are:
(1) Natural Selection
(2) Method of Genetic Drift
(3) Gene Variation on Mutation
(4) Geographical and environmental factors

Related Theory
Specialtion is the process by which new species form. It occurs when groups in a species become reproductively isolated and diverge.

(D) Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings?

Question 4.
When Simran visited the hospital, maternity ward to see her little brother born just a day before, she was pleasantly surprised to see so many new born babies in the hospital nursery. So, she thought, how many of these are male babies and how many are female?

The genetic makeup of a male embryo is determined by
(a) The X chromosome in the zygote
(b) The Y chromosome in the zygote
(c) The cytoplasm of the germ cell which determines the sex
(d) Sex is determined by chance
(b) The Y chromosome in the zygote
Explanation: A chiLd who inherits an X chromosome from her father wilt be a girL and the one who inherits a Y chromosome from him will be a boy. Thus the maleness of a chiLd is determined by the presence of the Y chromosome in the zygote inherited from the father.

Question 5.
In the F2 generation of a cross, progeny having different traits are produced in the ratio 3:1.
(A) State whether it is a monohybrid cross or a dihybrid cross? Give one example of such a cross.
(B) Exchange of genetic material takes place in:
(a) Vegetative reproduction
(b) Asexual reproduction
(c) Sexual reproduction
(d) Budding
It is a monohybrid cross.

Example: when two hybrids tall Pea plants crossbreed with each other they will produce three tall plants and one dwarf planet in the F2 generation.

(C) A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because:
(a) Tallness is the dominant trait
(b) Shortness is the dominant trait
(c) Tallness is the recessive trait
(d) Height of pea plant is not governed by gene ‘T’ or ‘t’

Question 6.
Observe the ears of all the students in the class. The lowest part of the ear, called the earlobe, is closely attached to the side of the head in some of us, and not in others. Free and attached earlobes are two variants found in human populations.

Prepare a list of students having free or attached earlobes and calculate the percentage of students having each. Find out about the earlobes of the parents of each student in the class. Correlate the earlobe type of each student with that of their parents. Based on this evidence, suggest a possible rule for the inheritance of earlobe types.
The percentage of people having free earlobes and attached earlobes is shown below:

(A) Based on the findings in the NCERT activity, it can be concluded that:
(II) The gene responsible for free earlobe may be dominant or recessive.
(III) The gene responsible for attached earlobe may be dominant or recessive.
(IV) The gene responsible for attached earlobe is recessive.
Select the correct statements.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)

(B) The earlobes of a child whose parents have free earlobes will be:
(a) Free earlobe
(b) Attached earlobe
(c) Can be free or attached earlobe
(d) Neither free nor attached
(B) (c) Can be free or attached earlobe

Explanation: Parents with free earlobes can have both a copy of the dominant and recessive allele and they may give birth to a baby with free or attached earlobes.

(C) The shape of the earlobe in an offspring is determined by:
(a) Variation
(b) Chromosome
(c) DNA
(d) Gene

(D) Mrs. and Mr. Sharma have six children. Three of them have attached eartobes Like their father, and the other three have free earlobes like their mother.
Taking F for free earlobes and f for attached earLobes, seLect the row containing the correct genotype of parents and children from the table below:

(b) Mrs. Sharma: Ff; Mr. Sharma: Ff; Children with free earlobes: Ff; Children with attached earlobes: ff

Explanation: All of the individuals with attached earlobes must be ff. AIL of the individuals with free earlobes can be FF or ff. In this particular case, the parent having free earlobe has children who have attached earlobes, so that parent must have an f, and is thus Ff. And all of the children have one parent with attached earlobes, so they must also all have at Least one f, and are thus Ff. So the answer is, Mr. Sharma is ff, Mrs. Sharma is Ff. The three chiLdren with attached earlobes are ff, and the three with free earlobes are Ff.

(E) A child has attached earlobes.
Select the most appropriate statement regarding the earlobe of his/her parents.
(a) Earlobes of either parent may be attached or free.
(b) Both parents have attached earlobes.
(c) One parent has attached earlobes
(d) Cannot be determined.

Question 7.
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.

Charles Darwin popularized the term “natural selection”, contrasting it with artificial selection, which in his view is intentional, whereas natural selection is not.

Natural selection can cause microevolution (change in allele frequencies), with fitness-increasing alleles becoming more common in the population. Fitness is a measure of reproductive success (how many offspring an organism leaves in the next generation, relative to others in the group). Natural selection can act on traits determined by alternative alleles of a single gene, or on polygenic traits (traits determined by many genes). Natural selection on traits determined by multiple genes may take the form of stabilizing selection, directional selection, or disruptive selection.
(A) Which of the following are examples of natural selection?
(I) In an ecosystem, lizards that had long legs could climb better to avoid floods and reach food.
(II) Insects become resistant to pesticides very quickly, sometime in one generation and if an insect is resistant to the chemical, most of the offspring will also be resistant.
(III) Cultivation of wild cabbage as a food plant, and generation of different vegetables from it
(IV) Dog breeding for various desired characteristics.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (IV)
(d) (I), (II) and (III)

(B) Natural selection acts on an organism’s:
(a) Environment
(b) Chromosome
(c) Phenotype
(d) Genotype

(C) Imagine a population of brown and white rabbits, whose coat color is determined by dominant brown (B) and recessive white (b) alleles of a single gene. A predator such as a hawk can see white rabbits more easily than brown rabbits against the backdrop of a grassy field.
What is likely to happen? Select the incorrect answer:
(a) Brown rabbits are more likely than white rabbits to survive hawk predation.
(b) The b alleles may disappear from the population after several generations due to selection.
(c) The next generation will probably contain a higher frequency of B alleles.
(d) The next generation will probably contain a higher frequency of b alleles.
(d) The next generation will probably contain a higher frequency of b alleles.

Explanation: Natural selection can shift allele and phenotype frequencies to make a population better-suited to its environment. If we imagine that half of the white rabbits (but none of the brown rabbits) are eaten by hawks, then the frequency of B allele will increase.

Natural selection acts on phenotypes, not genotypes, as a hawk can tell a brown rabbit from a white rabbit, but it can’t tell an BB rabbit from a Bb rabbit.

(D) Humans have, over more than two thousand years, cultivated wild cabbage as a food plant, and generated different vegetables from it by selection.
Select the row containing incorrect information.

 Desirable Characteristic Name of Vegetable Evolved from Wild Cabbage Short distances between leaves Cabbage For sterile flowers Kale For arrested flower development Broccoli For swollen parts Kohlrabi

(b) Desirable characteristic: For sterile flowers: Name of vegetable evolved from wild cabbage: Kale

Explanation: For sterile flowers, man of made cauliflower and for leafy vegetable, made kale.

(E) In a habitat there are red bugs and green bugs. The birds prefer the taste of the red bugs, so soon there are many green bugs and few red bugs. The green bugs reproduce and make more green bugs and eventually there are no more red bugs.
The above is an example of:
(a) Natural selection
(b) Genetic drift
(c) Geographical isolation
(d) Speciation

Question 8.
X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males (who are necessarily homozygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation. Females with one copy of the mutated gene are carriers. X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome.

In humans, inheritance of X-linked recessive traits follows a unique pattern as shown below:

The first is that affected fathers cannot pass x-linked recessive traits to their sons because fathers give Y chromosomes to their sons. Second, x-iinked recessive traits are more commonly expressed in males than females.
This is due to the fact that males possess only a single X chromosome, and therefore require only one mutated X in order to be affected. The last pattern seen is that x-linked recessive traits tend to skip generations, meaning an affected grandfather will not have an affected son, but could have an affected grandson through his daughter.

(A) In the cross shown above, if the father is unaffected and mother is also unaffected, but mother is a carrier (X-linked recessive allele present), then which of the following statements are correct about their children:
(I) Both sons will be unaffected but will be carriers.
(II) One son will be unaffected and one son will be affected.
(III) Both daughters will be unaffected
(IV) One daughter will be unaffected and one daughter will be affected.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
(b) Both (II) and (III)

Explanation: Females have two X chromosomes while males have one X and one Y chromosome. Carrier females who have only one copy of the mutation do not usually express the phenotype. So, the son who receives the X chromosome containing the dominant allele will be unaffected whereas the son who receives X chromosome containing the recessive allele will be affected. Both daughters will be unaffected, but the daughter who receives the recessive allele from her mother will be carrier.

This means that males affected by an x-linked recessive disorder inherited the responsible X chromosome from their mothers.

Women possess two X chromosomes and thus must receive two of the mutated recessive X chromosomes (one from each parent). A popular example showing this pattern of inheritance is that of the descendants of Queen Victoria and the blood disease hemophilia.

(B) Study the cross shown above and select the row containing incorrect information:

(a) can appear in both males and females
(b) are only found in males
(c) are only found in females
(d) appear only in F2 generation

(D) X-linked recessive traits are more commonly expressed in males than females because:
(a) Females have both X chromosomes which will be mutated at the same time
(b) Males possess a Y chromosome which can be mutated
(c) Males possess only a single X chromosome, and therefore require only one mutated X in order to be affected
(d) Chances of mutation of both X chromosomes in females is very low

(E) Insects also follow an XY sex- determination pattern and like humans, Drosophila males have an XY chromosome pair and females are XX. Eye color in Drosophila was one of the first X-linked traits to be identified. In fruit flies, the wild-type eye color is red (XW) and is dominant to white eye color (Xw).
In a cross between a white-eyed female fruit fly and red-eyed male, what percent of the female offspring will have white eyes? (White eyes are X-linked, recessive)
(a) 100 %
(b) 50 %
(c) 25 %
(d) 0 %
(d) 0%

Explanation: The genotype of a white-eyed female fruit fly will be XWXW and of red-eyed male will be XWY. When we cross them, the genotype of offspring will be:

XWXW (Red eyed female), X (White-eyed male), XWXW (Red-eyed female) and XWY (white-eyed male).
All of the females are thus red-eyed and heterozygous. All of the males are white-eyed and hemizygous.

Question 9.
In mice, black coat colour (B) is dominant over brown coat colour (b), and a solid pattern (S) is dominant over white spotted (s). Colour and spots are controlled by genes that assort independently. A homozygous (both alleles identical) black, spotted mouse is crossed with a homozygous brown, solid mouse.
(A) The genotypes of the parents is:
(a) Bbss and bbSS
(b) BBss and bbSs
(c) BbSs and BbSs
(d) BBss and bbSS

(B) Select the incorrect statements regarding the F1 progeny obtained:
(I) Phenotype of all mice of F1 generation is brown coat with solid pattern.
(II) Phenotype of all mice of F1 generation is black coat with solid pattern.
(III) Genotype of all mice of F1 generation is BbSs.
(IV) Genotype of all mice of F1 generation is BBSs.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (II) and (IV)
(d) Both (I) and (IV)
(d) Both (I) and (IV)

Explanation: Genotype of the homozygous black, spotted mouse is BBss and of the homozygous brown, solid mouse is bbSS.
When these are crossed, all F1 progeny will be black coat with solid pattern (BbSs) as gametes of homozygous black, spotted mouse will be Bs and of homozygous brown, solid mouse is bS.

(C) The table below shows the phenotypic ratio of F2 generation when mice of F1 generation are crossed with each other.
Select the row containing correct information:

(D) From the cross mentioned in (B) above, it can be concluded that:
(a) The phenotype of progeny is independent of inherited genes.
(b) The black/brown colour of coat and solid/spotted pattern are inherited independently.
(c) The genotype of progeny does not decide the phenotype.
(d) The phenotype and genotype of progeny are independently inherited.
(b) The black/brown colour of coat and solid/spotted pattern are Inherited independently.

Explanation: The genes responsible for coLour (black or brown) and spotting (solid pattern or spotted) are assorted independently.

(E) Suppose a test cross is carried out by mating FI mice with brown, spotted mice. The percentage of progeny having black coat with solid pattern will be;
(a) 75 %
(b) 50 %
(c) 25 %
(d) 0 %

Question 10.
Remember the Hindi film Ghajini where Aamir Khan had sported a new hairstyle? It became a rage and later, several boys started to experiment with their hairstyle in unique ways.

From the list given below, select the character which can be acquired but not inherited:
(a) Colour of eyes
(b) Colour of skin
(c) Size of body
(d) Nature of hair

Question 11.
A big challenge with species conservation is trying to limit and reduce the negative genetic effects of small or isolated populations. Founder’s effect or bottleneck effect can lead to small populations which are highly susceptible to genetic drift. This means there is a serious reduction in genetic variation within the population, making that population less able to adapt to new selective pressures (“Bottleneck and founder effects”). Even if the species’ numbers were to rebound, the new generations would only carry the limited set of alleles passed down by the small population.

A population bottleneck is an event that drastically reduces the size of a population. The bottleneck may be caused by various events, such as an environmental disaster, the hunting of a species to the point of extinction, or habitat destruction that results in the deaths of organisms. The population bottleneck produces a decrease in the gene pool of the population because many alleles, or gene variants, that were present in the original population are lost. Due to the event, the remaining population has a very low level of genetic diversity, which means that the population as a whole has few genetic characteristics.

(A) Select the correct statements:
(I) A population bottleneck decreases genetic variation in a species or subspecies.
(II) Gene flow increases genetic diversity by introducing new alleles into the population.
(III) Mutation decreases genetic diversity in a population.
(IV) Species can become extinct if genetic diversity recovers after the bottleneck.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) (I), (II) and (IV)

(B) Which of the following statements is true?
(a) Gene pool frequencies do not change as a result of migrations in or out of a population.
(b) Gene flow occurs only as a result of migrations.
(c) Gene flow can cause new alleles to enter a population’s gene pool.
(d) Gene flow is possible only in aquatic ecosystem.
(c) Gene flow can cause new alleles to enter a population’s gene pool.

Explanation: Since gene flow alters the recipient population’s gene pool, it causes evolution independent of any other evolutionary mechanism.

(C) Which of the following is not true of genetic drift?
(a) It can lead to alleles being fixed in a population
(b) It results from the random transmission of alleles from parents to offspring in a population
(c) It can lead to loss of alleles from a population
(d) It can increase the genetic diversity of a population

(D) In a population where the allele frequency shifts by random chance, the mechanism of evolution at work is:
(a) mutation
(b) genetic drift
(c) natural selection
(d) migration
(b) genetic drift

Explanation: Genetic drift occurs as a result of chance events causing changes in the allele frequency of a population. It doesn’t favor the fittest individuals, but occurs at random.

(E) Mutation may be described as:
(a) Continuous genetic variation
(b) Phenotypic change
(c) Discontinuous genetic variation
(d) Change due to hybridization

Question 12.
When a friend showed Uma two photographs and asked her to identify the relation between the persons shown in the photograph, she immediately replied that the photographs are of identical twins as they had identical features. But to her surprise, the photograph was of a father when he was a kid and of his daughter. The similarity in their features was remarkable!

Cellular DNA is the information source for making proteins in the cell. As genes are responsible for controlling various processes in an organism and are made up of DNA, we can say that DNA is the carrier of basic genetic information in organisms.

Question 13.
Speciation, the formation of new and distinct species in the course of evolution. Speciation involves the splitting of a single evolutionary lineage into two or more genetically independent lineages. Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics. The demands of a different environment or the characteristics of the members of the new group will differentiate the new species from their ancestors.
There are many hypotheses about how speciation starts, and they differ mainly in the role of geographic isolation and the origin of reproductive isolation (the prevention of two populations or more from interbreeding with one another).

(A) Select the incorrect statement.
Speciation is possible in isolated populations of the parent species because:
(a) There will be an accumulation of different changes in each sub-population due to genetic drift.
(b) Natural selection may operate differently in these different geographic locations.
(c) isolated populations are no longer able to interbreed.
(d) Increased gene flow
(d) Increased gene flow

Explanation: Speciation is possible when the parent species is subdivided into subpopulations. Each sub-population has a different gene pool and accumulation of different changes due to genetic drift. Moreover, different variations may be selected in the subpopulations by environmental factors. Eventually, the organisms belonging to the sub-populations may no longer be able to interbreed. However, if gene flow decreases, then the groups will evolve along separate paths.

(B) Two separate squirrel species inhabit the north and south rims of the canyon when Arizona’s Grand Canyon formed. This is an example of:
(a) Genetic Drift
(b) Geographical isolation
(c) Natural selection
(d) Variation

(C) New species may be formed if
(I) DNA undergoes significant change in germ cells
(II) Chromosome number changes in the gamete
(III) There is no change in the genetic material
(IV) Mating is no longer possible
(a) Both (I) and (III)
(b) Both (II) and (IV)
(c) (I), (II) and (III)
(d) (I), (II) and (IV)
(d) (I), (II) and (IV)

Explanation: New species may be formed due to significant change in DNA such that the organisms are no longer able to inter breed. Then, a new species is said to have been formed.

(D) Wild cabbage has evolved into new varieties like cabbage, broccoli and cauliflower by
(a) genetic drift
(b) natural selection
(c) reproductive isolation
(d) artificial selection

(E) Imagine a situation in which a population extends over a broad geographic range, and mating throughout the population is not random. Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range.

Which of the following can lead to the formation of a new species in such a situation?
Select the most appropriate answer in the given context.
(a) Geographical isolation
(b) Reduced gene flow
(c) Increased gene flow
(d) Genetic drift

Question 14.
When Priyanka went to the market to buy some pulses, she was quite surprised when the shopkeeper mentioned the different varieties of pea. There was green and round variety as well as yellow and wrinkled and also yellow and round varieties!

Round and green seeds of pea plant were crossed with wrinkled and yellow seeds. Progeny of F1 generation were all having round and green seeds. These F1 progenies were used to generate F2 progeny. Select the row containing incorrect observation or remarks:

 Observation Remarks (a) Genotype of parents of F1 progeny was RRyy (Round, green) and rrYY (Wrinkled, yellow) Roundness and yellow were dominant as all F1 progeny had round and yellow seeds (b) Genotype of 50% F1 progeny was RRYY and RrYy for the remaining 50% F1 progeny. As alt F1 progeny had round/yellow seeds, roundness and yellow were dominant. (c) Some F2 progeny showed new combinations The round seed/ wrinkled seed trait and yellow! green trait are independently inherited. (d) Phenotype ratio of F2 progeny was 9:3:3:1 9 (round/yellow) 3 (round green) 3 (wrinkled yellow) 1 (wrinkled green)

(b) Observation: Genotype of 50% F1 progeny was RRYY and RrYy for the remaining 50% F1 progeny: Remarks: As all F1 progeny had round/yellow seeds, roundness and yellow were dominant.

Question 1.
Mendel took tall pea plants and short pea plants and produced F1 progeny through cross-fertilisation. What did Mendel observe in the F1 progeny?
When Mendel cross-fertilized tall pea plants and short pea plants, he observed that all plants in the F1 progeny were tall.

Related Theory

• When these F1 progeny are self crossed, he observed that the F2 progeny are not all tall. The ratio of tall plants to dwarf plants comes to be approximately 3:1.
• This indicates that both the tallness (T) and shortness (t) traits were inherited in the F1 plants, but only the tallness trait was expressed.
• Above experiment led Mendel to propose that two copies of factor (now called genes) controlling traits are present in sexually reproducing organisms.
• Traits like T which are expressed are called dominant traits, while traits like’t’ are called recessive traits.

Question 2.
How is the normal number of chromosomes restored in the progeny of sexually reproducing organisms?
Each cell has two copies of each chromosome, one each from the male and female parents. Each germ cell or gamete takes one chromosome from each pair and when two germ cells combine, the original number of chromosomes is restored in the progeny.

Question 3.
Do all variations in a species have equal chances of surviving in the environment in which they find themselves?
No, all variations in a species do not have equal chances of surviving in the environment in which they find themselves. Depending upon the nature of variations, each individual would have different advantages of survival.

## Online Education for Life Processes Class 10 MCQs Questions with Answers

Life Processes Class 10 MCQ Question 1.
If salivary amylase is lacking in the saliva, which of the following events in the mouth cavity wilL be affected?
(a) Proteins breaking down into amino acids
(b) Starch breaking down into sugars
(c) Fats breaking down into fatty acids and glycerol
(d) Absorption of vitamins
(b) Starch breaking down into sugars

Explanation: The process of digestion begins in the mouth. The mouth contains a digestive enzyme, salivary amylase. This enzyme breaks the starch molecules in the food, into maltose. The absence of amylase in the saliva thus affects the breakdown of starch into simpler sugar molecules.

Class 10 Life Processes MCQ Question 2.
In the excretory system of human beings, some substances in the initial filtrate such as glucose, amino acids, salts and water are selectively reabsorbed in:
(a) Urethra
(b) Nephron
(c) Ureter
(b) Nephron.

Explanation: A nephron is a filtering unit present in kidney. It has different parts like Bowman’s capsule, glomerulus and tubuLar region (Renal tubule). Glucose, amino acids and salts are selectively reabsorbed in tubular region.

Life Processes MCQ Class 10 Question 3.
Which part of alimentary canal receives bile from the liver?
(a) Stomach
(b) Small intestine
(c) Large intestine
(d) Oesophagus
(b) Small intestine

Explanation: Bile is secreted by the liver and is stored in the gall bladder from where it enters the small intestine via a common duct.

Related Theory
It performs two functions:

1. makes the food alkaline.
2. breaks the fats present in food into small globules by the process of emulsification.

MCQ On Life Processes Class 10 Question 4.
Pseudopodia are:
(a) small hair-like structures present on unicellular organisms.
(b) false feet developed in some unicellular organisms.
(c) long, tube-like structures coming out of the mouth.
(d) suckers which are attached to the walls of the intestines.

Class 10 Science Chapter 6 MCQ Question 5.
A few drops of iodine solution were added to rice water. The solution turned blue-black in colour. This indicates that the rice water contains:
(a) Complex proteins
(b) Simple proteins
(c) Fats
(d) Starch
(d) Starch

Explanation: Iodine solution is often used for testing the presence of starch in the food particles. When iodine is added to starch, it turns blue-black. Rice water contains starch, hence when iodine solution is added to rice water it turns blue-black.

MCQ Of Life Processes Class 10 Question 6.
which one of the following statements is correct about the human circulatory system?
(a) Blood transports only oxygen and not carbon dioxide.
(b) Human heart has five chambers.
(c) Valves ensure that the blood does not flow backwards.
(d) Both oxygen-rich and oxygen-deficient blood gets mixed in the heart.

Class 10 Life Process MCQ Question 7.
Anaerobic process:
(a) takes place in yeast during fermentation.
(b) takes place in the presence of oxygen.
(c) produces only energy in the muscles of human beings.
(d) produces ethanol, oxygen and energy.
(a) takes place in yeast during fermentation.

Explanation: (a) Anaerobic respiration (in absence of oxygen) in yeast is known as fermentation as ethanol (alcohol) carbon dioxide and 2 ATP molecules of energy is produced from glucose.

carbon dioxide + 2 ATP molecules of energy
(b) Aerobic respiration takes place in presence of oxygen and anaerobic in absence of oxygen.
(c) In muscles of human beings: Lack of oxygen or absence of oxygen results into the formation of lactic acid and very less amount of energy.
(d) Ethanol and carbon dioxide are produced. Energy is neither produced nor released.

MCQ Life Processes Class 10 Question 8.
When air is blown from mouth into a test tube containing Lime water, the lime water turns milky due to the presence of
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Water vapour

Ch 6 Science Class 10 MCQ Question 9.
Most of the digestion and absorption of the food takes place in the:
(a) small intestine
(b) liver
(c) stomach
(d) large intestine
(a) small intestine.

Explanation: Small intestine receives juices from liver, pancreas and walls of small intestine. Bite juice from liver emulsifies the fats and makes the medium alkaline. Pancreas and small intestine juices contain amylase, lipase and tryspin.

The function of these enzymes ore:

Class 10 Science Ch 6 MCQ Question 10.
Which of the foL[owing statement (s) is (are) true about respiration?
(I) During inhalation ribs move inward and the diaphragm is raised.
(II) In the alveoli, the exchange of gases takes place i.e. oxygen from alveolar air diffuses into bLood and carbon dioxide from the blood into the alveolar air.
(III) Haemoglobin has a greater affinity for carbon dioxide than oxygen.
(IV)Atveoti increases surface area for the exchange of gases.
(a) (I) and (IV)
(b) (II) and (III)
(c) (I) and (III)
(d) (II) and (IV)

Life Processes Class 10 MCQ With Answers Question 11.
Which is the correct sequence of air passage during inhalation?
(a) Nostrils → Larynx → Pharynx → Trachea → Lungs
(b) Nasal passage → Trachea → Pharynx → Larynx → Alveoli
(c) Larynx → Nostrils → Pharynx → Lungs
(d) Nostrils → Pharynx → Larynx → Trachea → Alveoli
(d) Nostrils → Pharynx → Larynx → Trachea → Alveoli

Life Process Class 10 MCQ Question 12.
During respiration, the exchange of gases take place in:
(a) Trachea and Larynx
(b) Alveoli of lungs
(c) Alveoli and throat
(d) Throat and larynx

MCQs Of Life Processes Class 10 Question 13.
Single circulation, i.e., blood flows through the heart only once during one cycle of passage through the body, is exhibited by:
(a) Labeo, Chameleon, Salamander
(b) Hippocampus, Exocoetus, Anabas
(c) Hyla, Rana, Draco
(d) whale, dolphin, turtle
(b) Hippocampus, Exocoetus, Anabas

Explanation: Fishes have two-chambered heart and exhibit single circulation, while three-chambered heart of amphibians and reptiles and four-chambered heart of birds and mammals exhibit double circulation.

MCQs On Life Processes Class 10 Question 14.
In which of the following vertebrate group/ groups, does heart not pump oxygenated blood to different parts of the body?
(a) Pisces and amphibians
(b) Amphibians and reptiles
(c) Amphibians only
(d) Pisces only
(d) Pisces only

Explanation: Fishes have only two-chambered heart and the blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body. Thus, blood goes only once through the heart in the fish during one cycle of passage through the body. Fishes take in water through their mouths and force it past the gills where the dissolved oxygen is taken up by blood.

Class 10 Science Life Process MCQ Question 15.
Which of the following statements about the autotrophs is incorrect:
(a) They synthesize carbohydrates from carbon dioxide and water in the presence of sunlight and chlorophyll
(b) They store carbohydrates in the form of starch
(c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight
(d) They constitute the first trophic level in food chains
(c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight Explanation: Autotrophs obtain the required carbon and energy requirements from carbon dioxide and Sunlight. They combine carbon dioxide and water to form carbohydrates.

Question 16.
Oxygen liberated during photosynthesis comes from:
(a) Water
(b) Chlorophyll
(c) Carbon dioxide
(d) Glucose

Question 17.
The blood leaving the tissues becomes richer in:
(a) Carbon dioxide
(b) Water
(c) Haemoglobin
(d) Oxygen
(a) Carbon dioxide

Explanation: The blood leaving the tissues becomes richer in carbon dioxide. When the oxygenated blood passes through the capillaries of the tissue, it gives oxygen to the body cells and takes carbon dioxide, produced during cellular respiration. Thus, it becomes richer in carbon dioxide.

Question 18.
The xylem in plants are responsible for:
(a) Transport of water
(b) Transport of food
(c) Transport of amino acids
(d) Transport of oxygen
(a) Transport of water
Explanation: Xylem tissues include tracheids, vessels, fibres and parenchyma and serve in the ascent of sap/water and minerals.

Related Theory
Phloem tissues comprised of four elements: sieve, companion cell, phloem fibres and phloem parenchyma. They serve in the translocation of organic nutrients.

Question 19.
Which of the following is an incorrect statement?
(a) Organisms grow with time.
(b) Organisms must repair and maintain their structure.
(c) Movement of molecules does not take place among cells.
(d) Energy is essential for life processes.

Question 20.
The internal (cellular) energy reserve in autotrophs is:
(a) Glycogen
(b) Protein
(c) Starch
(d) Fatty acid
(c) Starch

Explanation: The food prepared in the plant (autotrophs) by the process of photosynthesis is glucose that gets stored in various plant parts in the form of starch.

Question 21.
Choose the event that does not occur in photosynthesis.
(a) Absorption of light energy by chlorophyll
(b) Reduction of carbon dioxide to carbohydrates
(c) Oxidation of carbon to carbon dioxide
(d) Conversion of light energy to chemical energy

Question 22.
Choose the forms in which most plants absorb nitrogen:
(I) Proteins
(II) Nitrates and Nitrites
(III) Urea
(IV) Atmospheric nitrogen
(a) (I) and (II)
(b) (II) and (III)
(c) (III) and (IV)
(d) (I) and (IV)

Question 23.
The doctor measured Ravi’s blood pressure and said it is normal now. The range of Ravi’s blood pressure (systolic/diastolic) is likely to be:
(a) $$\frac{120}{80}$$ mm of Hg
(b) $$\frac{160}{80}$$ mm of Hg
(c) $$\frac{120}{60}$$ mm of Hg
(d) $$\frac{180}{80}$$ mm of Hg
(a) $$\frac{120}{80}$$ mm of Hg

Explanation: Blood pressure is denoted by two values: one value is above and the other value
is below. The value that is above is the systolic pressure and the one that is below is the diastolic pressure. A normal individual should maintain a systolic/diastolic pressure of $$\frac{120}{80}$$ mm of Hg.

Related Theory
Blood pressure is the force applied by the blood against the walls of the arteries. The blood pressure is of two types – systolic and diastolic. The blood pressure of a normal individual is 120/80 mm ofHg. If a person has less blood pressure than normal, he/ she is said to have low blood pressure.

If a person has more blood pressure than normal, he/ she is said to have high blood pressure.

Question 24.
If the structure marked X in the diagram given below is blocked, then which of the processes will not occur?

(a) Transpiration and respiration
(b) Transpiration, photosynthesis and respiration
(c) Respiration, transpiration and transportation
(d) Respiration and photosynthesis [Diksha]
(b) Transpiration, photosynthesis and respiration Explanation: Here, the structure marked as X is stomata.
Stomata are responsible for gaseous exchange in the plant. If they are blocked, the gaseous exchange will not take place.

Hence, the two important processes of the plant: photosynthesis and respiration do not take place. Stomata are also responsible for removing extra water present in the plants.

Hence, if blocked, the process of transpiration will also be affected.

Question 25.
Which of the following statement(s) is incorrect about transport in plants:
(I) The transport in the xylem is achieved by utilizing energy.
(II) Transpiration helps in the absorption of water and minerals from the roots to the leaves.
(III) The transport of soluble products of photosynthesis occurs in the phloem.
(IV) Besides water, the xylem also transports amino acids and other substances.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (III) and (IV)
(c) Both (I) and (IV)

Explanation: Transport of water and minerals in xylem takes place by the process of osmosis due to difference in ionic concentration in the soil and inside the root. Transpiration pull helps in the absorption of water to the taller parts of a plant during the daytime when the stomata are open. The phloem transports the soluble products of photosynthesis, amino acids and some other substances.

Question 26.
Which of the following statements are incorrect about aerobic respiration?
(I) The first step is the breakdown of glucose into pyruvate.
(II) Glucose is a six-carbon molecule and pyruvate is a three-carbon molecule.
(III) The breakdown of glucose take place in the mitochondria.
(IV) The breakdown of pyruvate using oxygen takes place in the cytoplasm.
(a) Both (I) and (III)
(b) Both (II) and (IV)
(c) Both (III) and (IV)
(d) (I), (III) and (IV)

Question 27.
A student noted the differences between blood and lymph in the following table. Select the row containing correct information:

(d) Blood: It flows through blood capillaries: Lymph: It flows through arteries

Explanation: Lymph drains into Lymph capillaries from the intercellular spaces which join to form large lymph vessels that finally open into larger veins.

Question 28.
Select the incorrect statement from the statements given below.
Waste products in plants:
(a) Are stored in the Golgi apparatus.
(b) Are stored in leaves that fall off.
(c) Are stored as resins and gums, especially in old xylem.
(d) Are excreted into the soil around them.
(a) Are stored in the Golgi apparatus.

Question 29.
Which of the following part of the human excretory system is under nervous control?
(a) Ureters
(b) Urethra
(d) Collecting duct

Explanation: The urinary bladder is a muscular structure that stores the urine until we get the urge to urinate. It is under nervous control.

Question 30.
In humans, the oxygen-rich blood from the lungs comes to the:
(a) Left atrium.
(b) Right atrium
(c) Left ventricle
(d) Right ventricle

Question 31.
Select the incorrect statement:
(a) The arteries have thick, elastic walls
(b) The veins have thin walls
(c) Veins have valves to ensure that blood flows in one direction only.
(d) Arteries have valves to ensure that blood flows in one direction only.
(d) Arteries have valves to ensure that blood flows in one direction only.

Explanation: Arteries do not have any valves as they carry blood away from the heart. They have thick and elastic walls as they bLood is under high pressure. Veins have valves to ensure that the blood flows in one direction only.

### Assertion Reasoning questions Class 10 Science Chapter 6

For the following questions two statements are given- one labeled Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is correct explanation of the assertion.
(b) Both (A) and (R) are true but R is not the correct explanation of the assertion.
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 32.
Assertion (A): Transpiration cools leaf surface.
Reason (R): Transpiration helps in translocation of sugar in plants. [Diksha]
(c) (A) is true but (R) is false.

Explanation: Transpiration is the process by which plants lose extra water off their surface with the help of the stomata of the Leaves. The plants usually lose water during very hot season. As a result, the temperature of the plant decreases and it cools down. However, transpiration does not help in translocation of food in the plants. Therefore, the assertion is true but the reason accompanied is false.

Related Theory
Transpiration is an important plant process. The three important tasks that are accomplished due to transpiration are:

1. Decrease in temperature of the plant: When the plants lose water, the temperature of the plant’s decreases and therefore, the plants cool down.
2. Transpirational pull: When plants lose water, an empty space is created in the plants. As a result, the minerals and water from the root are pulled up. This process is called transpirational pull.
3. Plant turgidity: Transpiration helps plants in maintaining the turgidity of the plants.

Question 33.
Assertion (A): The leaves which are partly green and partly white are called variegated leaves.
Reason (R): The green part of such a leaf contains chlorophyll but the writing part does not contain chlorophyll.

Question 34.
Assertion (A): Human beings have a complex respiratory system.
Reason (R): Human skin is impermeable to gases.
(b) Both (A) and (R) are correct but the R is not the correct explanation of the Assertion. Explanation: Human skin is impermeable to gas to minimise the loss of water from the skin.

Question 35.
Assertion (A): Autotrophs can produce food on its own.
Reason (R): Green plants can absorb the energy of sunlight that falls on the leaves.
(b) (A) is true but (R) is false.

Explanation: All the green plants are called autotrophs. This is due to the fact that the green plants make their own food from very simple substances like carbon dioxide and water that is present in the surroundings.

The green plants in a terrestrial ecosystem capture about 1% energy of sunlight that falls on their leaves and convert it to into food energy.

Question 36.
Assertion (A): Hydrochloric acid secreted in the stomach makes an acidic medium for the action of the enzyme pepsin.
Reason (R): Bile juice from liver will make the medium alkaline in the small intestine for the panereatic juices to act.

Question 37.
Assertion (A): The opening and closing of the pore is a function of the guard cells.
Reason (R): Stomatal pores are the site for an exchange of gases by diffusion.
(b) Both (A) and (R) are correct but the R is not the correct explanation of the Assertion.

Related Theory:
Tiny pores present on the surface of leaves of plants are called stomata. Each stomatal pore is surrounded by a pair of guard cells.

When water flows into the guard cells, they swell, become curved and cause the pore to open. Similarly when the guard cells lose water, they shrink and the stomatal pore closes.

Question 38.
Assertion (A): Respiration is an exothermic reaction.
Reason (R): Respiration is processes in which glucose combines with oxygen and decompose to carbon dioxide and water this reaction also release some energy.
(a) Both A and R are true, and R is correct explanation of the assertion.

Question 39.
Assertion (A): The inner lining of the small intestine does not have numerous finger-like projections called villi.
Reason (R): The villi increase the surface area for absorption.
(d) A is false, but R is true.

Explanation: The inner lining of the small intestine have numerous finger-like projections called villi and these villi increase the surface area for absorption. Thus A is false, but R is true.

Question 40.
Assertion (A): Oxygenated blood flows in the pulmonary artery.
Reason (R): Arteries have a narrow lumen.

Question 41.
Assertion (A): Glucose is absorbed in the small intestine and reabsorbed by the kidney tubules.
Reason (R): Maximum absorption of glucose takes place in the large intestine.
(c) A is true, but R is false.

Explanation: Glucose is absorbed in the small intestine and reabsorbed by the kidney tubules and its maximum absorption takes place in the small intestine. Thus A is true, but R is false

(Competency-Based Questions)

Question 1.
Gargi loved eating sugar candies. So, whenever she went to local melas or school trips, she would have only sugar candies.

Which is the first enzyme to mix with food in the digestive tract?
(a) Pepsin
(b) Cellulase
(c) Amylase
(d) Trypsin
(c) Amylase

Explanation: Food digestion process begins in the mouth. Mouth contains salivary gLands that secrete saliva. Saliva contains an important enzyme known as salivary amylase that breaks down starch into simple sugars. Pepsin is a protein-digesting enzyme. Stomach contains gastric glands that secrete mucus, hydrochloric acid and pepsin.

Question 2.
Raima joined aerobics classes in her neighbourhood along with her friend. On the very first day, her instructor told them to always do these exercises in a well-ventilated room. She later found out the reason why her instructor had said so

 Aerobic respiration Anaerobic respiration (a) It takes place In presence oxygen It takes place in of absence of oxygen (b) end products are carbon dioxide and water and energy End products are carbon dioxide, energy (c) Large amount of energy is released Less amount of energy is released (d) It takes Place in muscles cells It takes place in Mitochondria yeast and human

Question 3.
Why do we need carbohydrates in our diet? Carbohydrates are our body’s main source of energy. They help fuel the brain, kidneys, heart muscles, and central nervous system. For instance, fibre is a carbohydrate that aids in digestion, helps one feel full, and keeps blood cholesterol levels in check. Some of the food items rich in carbohydrates are Breads, grains, and pasta, Nuts and Legumes, Starchy Vegetables, Milk and yogurts, Fruits and Snack Foods.

What happens during digestion of carbohydrates?
(a) Specific hormones break down carbohydrates into simple sugar such as glucose.
(b) Specific enzymes break down carbohydrates into fatty acids and glycerol.
(c) Specific enzymes break down carbohydrates into simple sugar such as glucose.
(d) Specific hormones break down carbohydrates into fatty acids and glycerol.
(c) Specific enzymes breakdown carbohydrates into simple sugar such as glucose. Explanation: The digestion of food is the break down of complex food substances by the enzymes secreted by various parts of the digestive system. Hormones are secreted by the endocrine glands and act on specific targets.

Question 4.
Table A (Blood glucose chart)

Table B (Blood Report of Patient X and Y)

(A) Refer to Table B showing the blood report of the levels of glucose of patients X and Y. Infer the disease which can be diagnosed from the given data.
Diabetes

(B) Identify the hormone whose level in the blood is responsible for the above disease.

(C) Which one of the following diets would you recommended to the affected patient?
(a) High sugar and low fat diet.
(b) Low sugar and high protein diet.
(c) High Fat and low fiber diet.
(d) Low sugar and high fiber diet.
(d) low sugar high fibre diet

(D) Refer to Table A and suggest the value of the mean blood glucose level beyond which doctor’s advice is necessary:
(a) 180 mg/dL
(b) 115 mg/dL
(c) 50 mg/dL
(d) 80 mg/dL
180 mg/dL

Question 5.
Kidneys are vital organs for survival. In case of kidney failure an artificial kidney can be used. An artificial kidney is a device to remove nitrogenous waste products from the blood through dialysis.
(A) What are the functions of kidneys?
The functions of kidneys are:
(1) To remove nitrogenous waste from the blood.
(2) To maintain salt and water balance in the body.

(B) Name the filtration units present in kidneys.
The filtration units present in the kidneys are nephrons.

(C) What is the excretory product removed by kidneys from blood?

(D) Name two substances which are selectively reabsorbed from nephric filtrate into the blood.
Two substances which are selectively reabsorbed from nephric filtrate into the blood are glucose, amino acids, salts and a major amount of water. (Any two)

Related Theory:
Bowman’s capsules of nephrons acts as ultra filters. Blood flows inside the glomerular capillaries under pressure and water with dissolved molecules from blood plasma diffuses out into Bowman’s capsule. The fluid collected in the Bowman’s capsule as a result of ultrafiltration is called nephric filtrate.

Question 6.

Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, expands, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body. De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it expands. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation.

Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do. Valves ensure that blood does not flow backwards when the atria or ventricles contract.
(A) Name the organs of the circulatory system in human.
The various organs of the circulatory system in humans are: heart, arteries, veins and capillaries.

(B) Name the red pigment which carries oxygen in the blood.
The red pigment which carries oxygen in the blood is Haemoglobin.

(C) How many chambers are there in the heart of an amphibian?

(D) Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
It is necessary to separate the oxygenated blood from mixing with deoxygenated blood as mammals and birds have high energy needs because they constantly require energy to maintain their body temperature.

Question 7.
The haemoglobin level is expressed as the amount of haemoglobin in grams (g) per deciliter (di) of whole blood, a deciliter being 100 milliliters. The normal ranges for hemoglobin depend on the age and, beginning in adolescence, the gender of the person. The normal ranges are:

Based on the above table answer the following questions
(A) What does o Low haemoglobin Level mean?
A low haemoglobin level is rererred to as anemia or low red blood count.

Explanation: A lower than normal number of red blood ceLls is referred to as anaemia and hemoglobin evets reflect this number.

(B) How is oxygen transported in human beings?
Transport of oxygen: Hoemoglobin present in the red blood corpuscles takes up the oxygen from the oir in the lungs. It carries the oxygen to tissues which are deficient in oxygen before releasing it.

(C) Respiratory pigment in human body is
(a) Chlorophyll
(b) Water
(c) Blood
(d) Haemoglobin
(d) Haemoglobin

Explanation: Respiratory pigment in human body is haemoglobin.

(D) Which of the following is an important component of haemoglobin?
(a) Iron
(b) Sodium
(c) Calcium
(d) Magnesium

Question 8.
Two students performed the following activities to understand the conditions necessary for photosynthesis.
The first student took a potted plant with variegated leaves – for example, money plant or crotons. He first kept the plant in a dark room for three days and then kept it in sunlight for about six hours. He plucked a leaf from the plant and marked the green areas in it and traced them on a sheet of paper. He then dipped the leaf in boiling water for a few minutes. After this, he immersed it in a beaker containing alcohol and carefully placed the above beaker in a water-bath and heated till the alcohol began to boil.

He dipped the leaf in a dilute solution of iodine for a few minutes, then took out the leaf and rinsed off the iodine solution. He based his conclusions by observing the colour of the leaf and comparing this with the tracing of the leaf done in the beginning.

The second student took two healthy potted plants which were nearly the same size and kept them in a dark room for three days. He then placed each plant on separate glass plates. He placed a watch-glass containing potassium hydroxide by the side of one of the plants and covered both plants with separate bell-jars as shown in Fig. below.

He used vaseline to seal the bottom of the jars to the glass plates so that the set-up is air¬tight and kept the plants in sunlight for about two hours. He then plucked a leaf from each plant and checked for the presence of starch as in the first activity.

(A) The first student noted down the following changes in colour of leaf and colour of alcohol solution after dipping
the Ipaf in boiling alcohol. Select the correct observation:

 Colour of Leaf Colour of Alcohol Solution (a) Leaf becomes colourless No change in colour (b) No change in colour No change in colour (c) Leaf becomes colourless Alcohol solution turns green (d) No change in colour Alcohol solution turns green

(c) Colour of leaf: Leaf becomes colourless; Colour of alcohol solution: Alcohol solution turns green Explanation: The green leaf becomes colourless because on immersing green leaf in alcohol, chlorophyll responsible for its green colour gets dissolved in alcohol. The colour of the alcohol solution therefore turns green.

(B) The second student placed a watch glass containing potassium hydroxide in one bell jar as:
(a) Potassium hydroxide absorbs carbon dioxide gas present in the bell jar.
(b) Potassium hydroxide absorbs moisture present in the bell jar.
(c) Potassium hydroxide absorbs oxygen gas present in the hell jar.
(d) Potassium hydroxide reacts with carbon dioxide gas to form a compound.
(a) Potassium hydroxide absorbs carbon dioxide gas present in the bell jar. Explanation: As the student wants to show that carbon dioxide is essential for photosynthesis, he sealed both the bell jars with vaseline and placed potassium hydroxide in one bell jar as potassium hydroxide absorbs carbon dioxide gas present in the bell jar. The plant in this bell jar will not be able to perform photosynthesis as carbon dioxide has been removed from the bell jar.

(C) Given below are four statements regarding the conclusions of the activities performed by the two students:
(I) The first student concluded that carbon dioxide is essential for photosynthesis.
(II) The first student concluded that chlorophyll is essential for photosynthesis.
(III) The second student concluded that carbon dioxide is essential for photosynthesis.
(IV) The second student that water is essential for photosynthesis.
Select the correct statement(s):
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) (I), (III) and (IV)

(D) Select the incorrect statement:
When the decolorized leaf is dipped in iodine solution by the first student, he observes that:
(a) There are two color regions in the leaf which are reddish brown and blue-black.
(b) The earlier green parts of the leaf turned blue black
(c) The earlier yellow turned reddish brown.
(d) The entire leaf turned blue-black.

(E) Select the correct statement:
(a) The two leaves from the bell jars in the activity performed by the second student showed the presence of different amount of starch
(b) The second student used tape to seal the bottom of the jars to the glass plates.
(c) Both the students first dipped the leaves in boiling alcohol to kill a leaf and stop chemical reactions occurring in it.
(d) Plants are kept in the dark for three days to remove all the chlorophyll from the leaves.
(a) The two leaves from the bell jars in the activity performed by the second student showed the presence of different amount of starch

Explanation: In the first set up availability of C02 will be less for making starch by the plant leaves, as potassium hydroxide (KOH) absorbs the CO2. In second plant setup, the leaves will have more amount of starch. So. the amount of starch wilt be different in the two leaves.

Question 9.
In the first activity, a student Rudra took some freshly prepared lime water in two test tubes marked A and & He blew air through the lime water in test tube A. He then used a syringe or pichkari and passed air through the fresh lime water in test tube B.

In the second activity, another student Siya took some fruit juice or sugar solution and took this mixture in a test tube fitted with a one-holed cork and fitted the cork with ci bent glass rube. She dipped the free end of the glass tube into a test tube containing freshly prepared time water.

(A) Ridra recorded his observations below.
Select the correct observation.

 Test Tube A Test Tube B (a) No change observed Lime water turned milky immediately (b) Lime water turned milky immediately No change observed (c) Lime water turned milky immediately Lime water turned milky after a Long time (d) Lime water turned milky after a Long time Lime water turned milky immediately

(c) Test Tube A: Lime water turned milky immediately; Test Tube B: Lime water turned milky after a long time

Explanation: Lime water turns milky when carbon dioxide gas is passed through it as a white precipitate of calcium carbonate is formed when lime water (calcium hydroxide) reacts with carbon dioxide gas. Lime water turns milky in test tube A as the exhaled air is rich in carbon dioxide. Whereas, lime water takes a lot of time to turn milky in test tube B as the amount of carbon dioxide present in atmesphereic air is very less as compared to exhaled air and hence carbon dioxide is produced after a long time.

(B) Select the incorrect observation from the statements given below:
(I) The amount of carbon dioxide in atmospheric oir and exhaled air are equal
(II) Exhaled air contains more carbon dioxide as compared to atmospheric air.
(III) Atmospheric air contains more carbon dioxide as compared to exhaled air.
(IV)Lime water turned milky immediately in both the test tubes A and B.
(a) Both (I) and (IV)
(b) Both (II) and (IV)
(c) Both (I), (II) and (III)
(d) Both (I), (III) and (IV)
(d) Both (I), (III) and (IV)

Explanation: The amount of carbon dioxide is more in exhaled air and very less in the atmosphere. The lime water turns milky immediately in test tube A as the exhaled air contains large amount of carbon dioxide gas whereas it takes lot of time to turn milky in test tube B as fermentation by yeast is a very slow process.

(C) In the second activity, Siya observed that:
(a) Lime water in the test tube turned milky after some time
(b) Lime water in the test tube turned milky immediately
(c) No change observed in the coLour of Lime water
(d) Lime water in the test tube turned blue black
(a) Lime water in the test tube turned milky after some time

Explanation: The lime water becomes milky after some time as carbon dioxide is produced as a result of fermentation of sugar on mixing yeast. The other product formed is alcohol.

(D) Setect the correct statement:
It can be concluded that:
(a) Carbon dioxide is produced as a result of digestion of food in the first activity.
(b) Carbon dioxide is produced as a result of aerobic respiration in the first activity.
(c) Oxygen is produced as a result of aerobic respiration in the first activity.
(d) Lactic acid is produced as a resuLt of anaerobic respiration in the second activity.

(E) The products of fermentation in yeast are:
(a) Carbon dioxide and energy
(b) Lactic acid and energy
(c) Ethanol, carbon dioxide and energy
(d) Water, carbon dioxide and energy

Question 10.
The unfolding COVID-19 pandemic has led to a global crisis which threatens to become a health, economic and humanitarian disaster. COVID-19 or COronaVIrus Disease 2019 is the term used by the WHO to refer to disease caused by this virus. The virus was also called 2019-nCoV (or 2019 novel CoronaVirus) prior to being official named by the WHO. COVID-19 is predominantly a respiratory disease, with severity ranging from mild to fatal, and transmission mostly from the spread of respiratory droplets. SARS-CoV-2 is transmitted person-to-person, predominantly by respiratory droplet spread and contact, similar to the MERS and SARS corona viruses.

(A) Select the incorrect statement about the COVID-19 disease:
(a) COVID-19 disease is caused by a virus.
(b) It is a respiratory disease
(c) It is transmitted mostly by respiratory droplets.
(d) It can be cured by taking antibiotics.

(B) From the statements given below, identify the incorrect cause of the disease:

 Respiratory Disease Cause (a) Tuberculosis Infection of trachea (b) Emphysema Reduction of gas exchange area of the lungs (c) Asthma constriction of the bronchi and bronchioles (d) Pneumoria An infection of the alveoli

(a) Respiratory Disease: Tuberculosis;
Cause: Infection of trachea.

Explanation: Tuberculosis is a potentially serious infectious bacterial disease that mainly affects the lungs.The bacteria that cause TB are spread when an infected person coughs or sneezes.

(C) In the respiratory system, an extensive network of blood vessels is present in:
(a) Bronchioles
(b) Alveoli
(c) Trachea
(d) Pharynx
(b) Alveoli

Explanation: Within the lungs, the
passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood-vessels.

(D) Given below are four statements about respiration. Identify the correct statement (s).
(I) During inhalation, the chest cavity becomes larger.
(II) Exchange of gases takes place in the bronchioles.
(III) Alveoli increase surface area for exchange of gases.
(IV) Haemoglobin has greater affinity for carbon dioxide than oxygen.
(a) Both I and II
(b) Both II and III
(c) Both I and ill
(d) Both II and IV
(c) Both I and III

Explanation: During inhalation of air, our chest cavity or thoracic cavity expands. The exchange of gases takes place in the alveoli, which are balloon like structures in our lungs. These have very thin walls which are richly supplied with blood capillaries. Haemoglobin has a greater affinity for oxygen and isc arried by blood for oxygen and oxygen is carried by the blood to different parts as oxy haemoglobin, whereas carbon dioxide is transported in dissolved form.

(E) Which one of the following statements is false about the trachea?
(a) It has rings of cartilage
(b) it is covered by epiglottis
(c) It splits into the right and left lungs
(d) It is also called windpipe.

Question 11.
COVID-19 is a respiratory disease, one that especially reaches into your respiratory tract, which includes your lungs. Now, think of your respiratory tract as an upside-down tree. The trunk is your trachea, or windpipe. It splits into smaller and smaller branches in your lungs. At the end of each branch are tiny air sacs called alveoli. The new coronavirus travels down your airways. The lining can become irritated and inflamed. In some cases, the infection can reach all the way down into your alveoli.
(A) What is the function of alveoli?
(a) This is where SARS-CoV-2, the virus that causesCOVID-19 finally affects.
(b) This is where plasma, proteins and blood cells escapes inthe tissues
(c) This is where oxygen goes into your blood and carbon dioxide comesout.
(d) Alveoli carries fat and drains excessive fluid back into the blood.
(c) This is where oxygen goes into your blood and carbon dioxide comes out.

Explanation: Alveoli act as the passage gateway for the exchange of the gases between the surroundings and the body.

(B) Your blood oxygen level indicates how much oxygen your red blood cells are carrying. High blood oxygenation plays an essential role in ensuring that your muscles, brain and other organs receive the energy they need to function properly. That’s why it is so important to measure your current level and determine whether it is within an acceptable range.
Why is it important to measure your current oxygen level?
(a) To know how much blood is flowing
(b) To know how much oxygen is flowing in the blood.
(c) To know how your brain is working
(d) To know the heart rate

(C) The lungs are the organ most commonly affected by COVID-19. If large parts of the lungs are affected, people struggle to absorb enough oxygen and are admitted to hospital. Another severe effect is acute respiratory distress syndrome (ARDS) – also known as “wet lung”. This sees severe inflammation spread quickly throughout the lungs. People who develop this may need mechanical ventilation in an intensive care unit, sometimes for a prolonged period. COVID-19 has a further, unusual effect on the body. Compared to other respiratory viruses, it causes marked clotting in the small blood vessels of the lungs and other organs.
How are the lungs affected by COVID-19?
(A) Blood clotting
(B) Lack of oxygen
(C) Severe inflammation
Now choose the correct option.
(a) A and B only
(b) B and C only
(c) None of these
(d) A, B and C or either of these

(D) Haemoglobin is an iron containing respiratory pigment that carries oxygen through red blood cells. Presence of Haemoglobin gives metallic taste to the blood. Haemoglobin is an intracellular protein which acts as a primary vehicle for transporting 97% of oxygen in the blood.
Which is not true about Haemoglobin?
(a) It is a respiratory pigment.
(b) It has a high affinity for oxygen and carbon dioxide.
(c) it is present in RBCs.
(d) Its deficiency causes anaemia.
(b) It has a high affinity for oxygen and carbon dioxide.

Explanation: Haemoglobin has high affinity for carbon dioxide since it forms the coordinate complex between the Fe and C leading to resist the ability of the oxygen to carry the oxygen leading to various respiratory disorders.

(E) In the given picture, “A” represents
(a) Rings of cartilage which ensures that the air passage does not collapse while going into the lungs.
(b) Diaphragm which contracts and flattens upon inhalation.
(c) Alveoli where the exchange of gases can take place.
(d) Fine hairs for air filtration.

(a) Rings of cartilage which ensures that the air passage does not collapse while going into the lungs.

Question 12.
Multicellular organisms with small surface area to volume ratios need transport systems. Water and mineral salts are transported through a plant in xylem vessels. Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism.
The pattern of water uptake and loss by sunflower plant during 24 h is shown in the graph below:

The movement of sucrose and other substances like amino acids around a plant is called translocation. Translocation of organic solutes such as sucrose occurs through living phloem sieve tubes. Both xylem vessels and phloem sieve tubes show unique structural features which are adaptations to their roles in transport.

(A) Root pressure is maximum when
(a) Transpiration is very high and absorption is very low
(b) Transpiration is very low and absorption is very high
(c) Both transpiration and absorption are very high
(d) Both the absorption and transpiration are very low
(b) Transpiration is very low and absorption is very high

Explanation: At night, when there is no sunlight, transpiration is very low but the absorption of substances by roots is high.

(B) Select the row containing incorrect information:

 Cell Vascular Tissue (a) Vessels Xylem (b) Sieve tube Xylem (c) Tracheids Xylem (d) Companion cell Phloem

(b) Cell: Sieve tube: Vascular Tissue: Xylem.

Explanation: Xylem is the conducting tissue for water and minerals and consists of vessels, tracheids and xylem parenchyma. Phloem on the other hand transports the dissolved products of photosynthesis and consists of sieve tubes, phloem parenchyma and companion cells.

(C) Given below are some statements about transport in plants:
(I) Xylem transports water, amino acids and other substances in plants.
(II) Phloem transports soluble products of photosynthesis in plants.
(III) Transpiration helps in absorption of water.
(IV) Material like sucrose is transferred into phloem tissue using energy from ATP
Select the correct statement (s):
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (II) and (IV)
(d) (II), (III) and (IV)
(d) (II), (III) and (IV)

Explanation: Xylem transports water and minerals from the soil to different parts of the plant in upward direction.
PhLoem transports the soluble products of photosynthesis from the leaves to different parts of the plant by using energy from ATP. It also transports amino acids and other substances in plants. Transpiration is the loss of water by the aerial parts of the plant during day time which helps in creating a transpiration pull due to which water moves upward in xylem.

(D) The major driving force in the movement of water from ground to the root during day is:
(a) Osmosis
(b) Imbibition
(c) Transpiration pull
(d) Plasmolysis

(E) Water will be absorbed by the root hairs when the external medium is
(a) Isotonic
(b) Hypertonic
(c) Hypotonic
(d) Viscous

Question 13.
The food material taken in during the process of nutrition is used in cells to provide energy for various life processes. Diverse organisms do this in different ways – some use oxygen to break-down glucose completely: some use other pathways that do not involve oxygen.
(A) Name the two ways in which glucose is oxidised to provide energy in various organisms.
(a) Aerobic respiration and Anaerobic respiration
(b) Respiration and breathing
(c) Fermentation and breathing
(d) None of the above
(a) Aerobic respiration and anaerobic respiration

Explanation: The two ways through which glucose is oxidised to provide energy in various organisms is through the aerobic and anaerobic respiration. Aerobic respiration occurs during the presence of air., whereas the anaerobic respiration occurs in the absence of air.

(B) The characteristic processes observed in anaerobic respiration are
(I) Presence of oxygen
(II) Release of carbon dioxide
(III) Release of energy
(IV) Release of lactic acid
(a) A and B only
(b) A,B,C only
(c) B, C, D only
(d) D only

(C) Fatigue in muscles occurs due to
(a) Aerobic respiration
(b) Anaerobic respiration
(c) Anaerobic fermentation
(d) Breathing
(b) Anaerobic respiration

Explanation: In the anaerobic respiration the release of the carborl dioxide takes along with the release of the energy and lactic acid thus fatigue in the muscles occur due to this phenomenon.

(D) Break-down of pyruvate using oxygen takes place in the
(a) Mitochondria
(b) Cytoplasm
(c) Chloroplast
(d) Golgi apparatus

(E) In humans, however, we respire anaerobically when the heart and lungs cannot work fast enough to provide enough oxygen around the body to break down the glucose. This causes formation of:

(a) Ethanol
(b) Carbon dioxide
(c) Lactic acid
(d) All the above
(c) Lactic acid

Explanation: Lactic acid is formed when we respire anaerobically when the heart and lungs cannot work fast enough to provide enough oxygen around the body to break down the glucose.

Question 14.
Diabetes meilitus, usually caiLed diabetes, is a disease in which your body does not make enough insulin or cannot use normal amounts of insulin properly.

The kidneys play an important role in regulating *glucose homeostasis through utilization of glucose, gluconeogenesis, and glucose reabsorption. Glucose is freely filtered by the glomerulus. Glomerular filtration rate (GFR) represents the flow of plasma from the glomerulus into Bowman’s space over a specified period and is the chief measure of kidney function. Under normal conditions, ~ 180 g of glucose are filtered by the kidney each day. More than 99% of this glucose is reabsorbed by the proximal tubule, with < 0.5 g/day excreted in the urine of healthy adults. When the filtered glucose load exceeds the tubular maximum glucose reabsorptive capacity, excess glucose is excreted in the urine.

The physiological relationship between plasma glucose concentration and renal glucose flux (ie, filtration, reabsorption, and excretion) is shown below:

(A) The incorrect conclusion from the graph showing amount of glucose filtered by the kidneys is:
(a) The amount of glucose filtered by the kidneys increases in a linear manner with increasing plasma glucose concentration
(b) Under normal conditions in healthy individuals, nearly all filtered glucose is reabsorbed in the renal tubules
(c) The renal glucose reabsorption increases linearly with increasing plasma glucose concentration.
(d) There is a distinct deviation (the “splay”) from this linear relationship as the renal capacity to reabsorb glucose nears saturation.
(c) The renal glucose reabsorption increases linearly with increasing plasma glucose concentration.

Explanation: The renal glucose reabsorption increases linearly until a certain concentration of plasma glucose is present. After the saturation limit of glucose is reached, it does not change.

(B) The excretory system of human beings include
(a) A kidney, a ureter, a urinary bladder and a urethra
(b) A pair of kidneys, a ureter, a pair of urinary bladders, and a urethra
(c) A pair of kidneys, a pair of ureters, a urinary bladder and a urethra
(d) A pair of kidneys, a pair of ureters, a pair of urinary bladders and a urethra

(C) Which of the following statements) is correct about excretion in human beings?
(I) Kidneys are the primary excretory organs.
(II) Nitrogenous waste such as urea or uric acid are removed from blood in the kidneys.
(III) The basic filtration unit in the kidneys is a cluster of very thin- walled blood Capillaries.
(IV) Urine is stored in the urethra until the urge of passing it out.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) (I), (III) and (IV)
(d) (I), (II) and (III)
(d) (I), (II) and (III)

Explanation: The only incorrect statement is that urine is stored in the urethra, as urine is actually stored in the urinary bladder, which is a muscular organ and under our nervous control.

(D) The correct function of parts labelled ‘A’ and ‘B’ in the figure below is:

 Part ‘A’ Part ‘B’ (a) Filtration of blood Reabsorption of glucose, salts and amino acids (b) Reabsorption of glucose, salts and amino acids Filtration of blood (c) Reabsorption of hormones from blood Filtration of blood (d) Collection of urine Reabsorption of glucose,salts and amino acids

(a) part ‘A’ : Filtration of blood; part ‘B’ : Reabsorbtion of glucose, Salts and amino acids

Explanation: Part labelled A is the Bowman’s capsule which is a cup-like sac at the beginning of the tubular component of a nephron in the mammalian kidney. Fluids from blood in the glomerulus are collected in the Bowman’s capsule and further processed along the nephron to form urine.

Part labelled B is the tubular part of the nephron where some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine along the tube.

(E) The part labelled ‘A’ in the figure above is:
(a) Glomerulus
(b) Bowman’s Capsule
(c) Proximal tubule
(d) Distant convoluted tubule

Question 15.
Blood being a fluid connective tissue. Blood consists of fluid medium called plasma in which the cells are suspended. Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form. Oxygen is carried by the red blood corpuscles. Many other substances like salts are also transported by the blood. l/l/e thus need a pumping organ to push blood around the body, a network of tubes to reach all the tissues and a system in place to ensure that this network can be repaired if damaged. The force that blood exerts against the wall of a vessel is called blood pressure. This pressure is much greater in arteries than in veins. The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.
(A) Blood consists of a fluid medium called as:
(a) Plasma
(b) Red blood corpuscles
(c) White blood corpuscles
(d) Lymph
(a) Plasma

Explanation: Blood consists of the 90% water in the form of the ions and the dissolved state known as plasma.

(B) Oxygen is transported in the body by combining with:
(a) Haemoglobin and iron only
(b) Haemoglobin only
(c) Plasma, Haemoglobin and iron
(d) None of these

(C) The oxygenated blood is sent to different body parts by:
(a) Arteries
(b) Veins
(c) Heart
(d) Circulatory system
(a) Arteries

Explanation: Arteries carry the oxygenated blood that is the pure blood to the different parts of the body whereas the deoxygenated blood is carried by the veins from the different body parts back to the heart.

(D) In fish and men the pumping organ to push blood are
(a) 2 and 3 chambered respectively
(b) 2 and 4 chambered respectively
(c) 4 and 2 chambered respectively
(d) 2 and 2 chambered each
(b) 2 and 4 chambered respectively

Explanation: In fish and men the pumping organ to push blood is 2 and 4 chambered respectively in human’s two auricles and two ventricles are there for the separation of the oxygenated and the deoxygenated blood.

(E) The force that blood exerts against the wall of a vessel is
(a) More in arteries and less in vein
(b) More in veins and less in arteries.
(c) More in blood capillaries
(d) More in heart

Question 16.
The digestion in stomach is taken care of by the gastric glands present in the wall of the stomach. These release hydrochloric acid, a protein digesting enzyme called pepsin, and mucus. The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin. The mucus protects the inner lining of the stomach from the action of the acid under normal conditions. From the stomach, the food now enters the small intestine. The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act Bile juice from the liver accomplishes this in addition to acting on fats.
(A) In which medium Pepsin and trypsin are active:
(a) basic and acidic medium
(b) acidic and basic medium
(c) neutral medium
(d) sometimes acidic sometimes basic medium

(b) acidic and basic medium

Explanation: Pepsin works in the acidic medium and trypsin works in the basic medium to digest the proteins in stomach and in the intestine respectively.

(B) Enzyme pepsin helps in the digestion of:
(a) starch in mouth
(b) protein in stomach
(c) fat in stomach
(d) protein in pancreas
(b) protein in stomach

Explanation: Enzyme pepsin helps in the digestion of proteins in the stomach.

(C) The inner lining of the stomach is protected by
(a) enzyme pepsin
(b) mucus
(c) Hydrochloric acid
(d) Muscle

(D) Which statement is a valid conclusion based on the information in the graph –
(a) The maximum rate of human digestion occurs at about 45°C.
(b) The maximum rate of human respiration occurs at about 57°C.
(c) Temperature can influence the action of an enzyme.
(d) Growth can be controlled by enzyme

(E) Small Intestine receives the secretions from for complete digestion.
(a) Mouth and Stomach
(b) Stomach and liver
(c) Liver and Pancreas
(d) All the above
(C) Liver and Pancreas

Explanation: Small Intestine receives the secretions from the liver and pancreas for complete digestion.

Question 1.
Name an enzyme present in pancreaticjuice.
Lipase, Trypsin

Question 2.
If human urine is allowed to stand for sometime, it smells of ammonia, why?
Urea present in urine gets decomposed into ammonia by the action of bacteria. So it smells strongly of ammonia.

Related Theory
The purpose of making urine is to filter out waste products from the blood. Nitrogenous waste such as urea or uric acid are removed from blood in the kidneys.

Question 3.
Define parasitic nutrition. Name an organism having parasitic mode of nutrition.

Question 4.
On what factors does the direction of diffusion of carbon dioxide and oxygen depend in plants?
The direction of diffusion of carbon dioxide and oxygen in plants depends on the environmental conditions and the requirements of the plant. Carbon dioxide elimination is the major exchange activity at night, whereas oxygen release is the main activity at day time.

Question 5.
What is the role of rings of cartilage present in the throat?
The rings of cartilage present ;n the throat ensure that the air passage does not collapse.

Question 6.
What is the role of blood plasma?

Question 7.
Why do fishes die when taken out of water?
Fishes respire with the help of gills. Gills are richly supplied with blood capillaries and can readily absorb oxygen dissolved in water. Since fishes cannot absorb gaseous oxygen, they die soon after they are taken out of water.

Question 8.
What will happen to a plant if its xyiem is removed?
If the xyiem of a plant is removed, the upward movement of water and minerals will stop leading to wilting of leaves and ultimately the death of the plant as xyiem is a water¬conducting tissue in plants. It transports water and minerals from the roots to the different parts of the plant.

Question 9.
The pancreas of a person suddenly stopped functioning. How will digestion be affected in such a person?

## Online Education MCQ Questions for Class 10 Science Chapter 11 Human Eye and Colourful World with Answers

Check the below Online Education NCERT MCQ Questions for MCQ Questions for Class 10 Science Chapter 11 Human Eye and Colourful World with Answers with Answers Pdf free download. https://ncertmcq.com/mcq-questions-for-class-10-science-with-answers/

## Online Education for Human Eye and Colourful World Class 10 MCQs Questions with Answers

Human Eye And Colourful World Class 10 MCQ Question 1.
A student traces the path of a ray of light through a glass prism for different angles of incidence. He analyses each diagram and draws the following conclusion:
(I) On entering prism, the Lightray bends towards its base.
(II) light ray suffers refraction at the point of incidence and point of emergence while passing through the prism.
(III) Emergent ray bends at a certain angle to the direction of the incident ray.
(IV) White emerging from the prism, the Lightray bends towards the vertex of the prism.
Out of the above inferences, the correct ones are:
(a) (I), (II) and (III)
(b) (I), (III) and (IV)
(c) (II), (III) and (IV)
(d) (I) and (IV)
(a) (I), (II) and (III)

Related Theory:
In a prism, the ray of light from air into glass bends towards the normal. The ray of light from glass to air bends away from the normal. In both cases, when a ray of light passes through a prism, it bends towards the base of the prism.

Human Eye And Colourful World MCQ Question 2.
A clear sky appears blue, because:
(a) blue light gets absorbed in the atmosphere
(b) ultraviolet radiations are absorbed in the atmosphere
(c) violet and blue lights get scattered more than the lights of all other colours by the atmosphere
(d) lights of all other colours are scattered more than the violet and blue colour lights by the atmosphere

Human Eye Class 10 MCQ Question 3.
Which of the following statements is correct regarding the propagation of light of different colours of white light in the air?
(a) Red light moves the fastest.
(b) Blue light moves faster than green light.
(c) All the colours of the white light travel at the same speed.
(d) Yellow light moves with the mean speed as that of red and violet light.

Human Eye MCQ Class 10 Question 4.
In the following diagram, the correctly marked angles are:

(a) All
(b) Only ∠i, and ∠A
(c) ∠i, ∠r and ∠A
(d) ∠i, ∠A and ∠D

Human Eye And The Colourful World MCQ Question 5.
The bluish colour of water in the deep sea is due to:
(a) the presence of algae and other plants found in water
(b) reflection of the sky in the water
(c) scattering of light
(d) absorption of light by the sea
(c) scattering of light

Explanation: The bluish colour of water in the deep sea is due to scattering of light. The fine particles in water scatter mainly blue light having the shortest wavelength.

Related Theory:
Water appears blue because when white light from the Sun falls on the water molecules, only blue light is reflected and scattered and reaches our eyes.
The absorption of light by a molecule depends on the wavelength and the size of the molecule. A molecule absorbs light of a wavelength either equal to or greater than the order of the size of the object.
Since red, orange and yellow have longer wavelengths, they are absorbed by the water molecules, whereas blue, having a shorter wavelength, is scattered.

Colourful World Class 10 MCQ Question 6.
During the experiment, to trace the path of ray of light through the glass prism, students reported the following observations:
(I) The ray of light from air to glass at the first refracting surface bends away from the normal after refraction.
(II) At the second refracting surface, light rays entered from air to glass.
(III) Lightray suffers two refractions on passing through a prism and in each refraction it bends towards the base of the prism.
(IV) Lightray suffers two refractions on passing through a prism. In first refraction, it bends away from the normal while in the second refraction it bends towards the normaL
The correct observation is/are:
(a) (I) and (II) only
(b) (III) only
(c) (II) and (IV) only
(d) (I) and (IV) only

Class 10 Human Eye And The Colourful World MCQ Question 7.
In an experiment to trace the path of a ray of light through a triangular glass prism, a student would observe that the emergent ray
(a) is parallel to the incident ray.
(b) is along the same direction of incident ray.
(c) gets deviated and bends towards the thinner part of the prism.
(d) gets deviated and bends towards the thicker part (base) of the prism.

Class 10 Science Chapter 11 MCQ Question 8.
In the following ray diagram the correctly marked angle are:

(a) ∠i, and ∠e
(b) ∠A and ∠D
(c) ∠i, ∠e and ∠D
(d) ∠r, ∠A and ∠D
(d) ∠r, ∠A and ∠D

Human Eye And Colourful World Class 10 MCQ With Answers Question 9.
A person cannot see distinctly the objects kept beyond 2 m. This defect can be corrected by using a lens of power:
(a) + 0.5 D
(b) – 0.5 D
(c) + 0.2 D
(d) – 0.2 D

MCQ Of Human Eye Class 10 Question 10.
A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his textbook. Which of the following statements is correct?
(a) The near point of his eyes has receded away.
(b) The near point of his eyes has come closer to him.
(c) The far point of his eyes has come closer to him.
(d) The far point of his eyes has receded away.
(a) The near point of his eyes has receded away.

Explanation: The student can see the object which is far from him but can’t see nearby objects. It means that the near point of his eyes has receded away. This condition is known as hypermetropia or farsightedness.

MCQ On Human Eye Class 10 Question 11.
When light rays enter the eye, most of the refraction occurs at the:
(a) crystalline lens
(b) the outer surface of the cornea
(c) iris
(d) pupil
(b) the outer surface of the cornea

Explanation: Light enters the eye through a thin membrane called the cornea. It causes most of the bending of incident light rays, i.e. refraction, to make them converge which in turn causes image formation on the retina.

Ch 11 Science Class 10 MCQ Question 12.
The focal length of the eye lens increases when eye muscles:
(a) are relaxed and the lens becomes thinner
(b) contract and the lens becomes thicker
(c) are relaxed and the lens becomes thicker
(d) contract and the lens becomes thinner

The Colourful World Class 10 MCQ Question 13.
Which of the following statements is correct?
(a) A person with myopia can see distant objects clearly.
(b) A person with hypermetropia can see nearby objects clearly.
(c) A person with myopia can see nearby objects clearly.
(d) A person with hypermetropia cannot see distant objects clearly.
(c) A person with myopia can see nearby objects clearly.

Explanation: Myopia is also termed as short-sightedness. A person suffering from myopia can see nearby objects clearly but not the distant objects. Whereas hypermetropia is termed as long-sightedness. A person suffering from hypermetropia can see distant objects clearly but not the nearby objects.

Class 10 Science Ch 11 MCQ Question 14.
Person suffering from cataract has:
(a) elongated eyeball
(b) excessive curvature of eye lens
(c) weakened ciliary muscles
(d) opaque eye Lens

Human Eye And The Colourful World Class 10 MCQ Question 15.
When we enter a dark room coming from outside, immediately the things inside the room do not appear clear to our eyes. This is because:
(a) pupils do not open at all in the dark.
(b) pupils take time to adjust.
(c) light travels slower in a dark room.
(d) pupils open very quickly in the dark.

MCQ Of Colourful World Class 10 Question 16.
The phenomena of light responsible for the working of the human eye is:
(a) reflection
(b) refraction
(c) power of accommodation
(d) persistence of vision

MCQs On Human Eye And Colourful World Question 17.
The sky appears dark to passengers flying at very high altitudes mainly because:
(a) Scattering of light is not enough at such heights.
(b) There is no atmosphere at great heights.
(c) The size of molecules is smaller than the wavelength of visible light.
(d) The light gets scattered towards the earth.
(a) Scattering of light is not enough at such heights.

Explanation: At higher altitude either the atmospheric medium is very rare or there are no particles present/ no atmosphere, thus the scattering of light taking place is not enough at such heights or no scattering of sunlight takes place. Hence, the sky appears dark to the passengers flying at very high altitude.

MCQ Of Human Eye And Colourful World Question 18.
Given below are some common observations related to optics. Select the row containing incorrect observations and its reason.

 Observation Reason (a) Colour of water in deep sea Scattering of light (b) Apparent position of stars Atmospheric refraction (c) Fishes appear higher than their actual depth Diffraction of light (d) Spectrum seen on soap bubbles Dispersion of light

(c) Observation: Fishes appear higher than their actual depth, Reason: Diffraction of light

Explanation: Fishes appear higher than their actual depth due to the refraction of light as light travels from water, an optically denser medium, to air, a rarer medium. Diffraction of light refers to the phenomena of bending of light around corners.

Class 10 Physics Human Eye And The Colourful World MCQ Question 19.
The defective eye of a person has near point 0.5 m and far point 75 cm. The table below lists the type of corrective lens and its power required for reading purposes and for seeing distant objects.

Select the row containing the correct information:

 For reading purpose For seeing distant objects (a) Concave lens of  power – 0.5 D Convex lens of power + 0.75 D (b) Convex lens of power +0.5 D A concave lens of power – 0.75 D (c) Convex Lens of power + 0.5 D Concave Lens of power-1.33 D (d) Convex Lens of power + 2.0 D Concave Lens of power -1.33 D

MCQ Questions For Class 10 Human Eye And Colourful World Question 20.
A 55-year-old near-sighted person wears spectacles with a power of – 2.5 D for distance viewing. His doctor prescribes a correction of + 2.0 D in the near-vision section of his bifocals. This is measured relative to the main part of the lens.

Select the correct statements:
(I) The focal length of the distance-viewing part of the lens is – 40 cm.
(II) The focal length of the near-vision part of the lens is + 50 cm.
(III) The focal length of the distance-viewing part of the lens is + 50 cm.
(IV) The focal length of the near-vision part of the lens is – 40 cm.
(a) Both (I) and (II)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (III) and (IV)

Class 10 Science Human Eye And Colourful World MCQ Question 21.
A beam of white light falling on a glass prism gets split up into seven colours marked 1 to 7 as shown in the diagram
Select the incorrect statements regarding the colours marked from 1 to 7:
(I) The colour at position marked 7 and 5 are similar to the colour of the blood and colour of gold metal respectively.
(II) The colour at position marked 1 and 3 are similar to the colour of the blood and colour of gold metal respectively.
(III) The colour at position marked 3 and 4 are similar to the colour of the sky and colour of leaves in plants respectively.
(IV) The colour at position marked 5 and 4 are similar to the colour of the sky and colour of leaves in plants respectively.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) Both (II) and (IV)

Question 22.
The defects of vision hypermetropia and myopia can be corrected by:
(a) Concave and a plano-convex lens
(b) Concave and convex lens
(c) Convex and concave lens
(d) Plano-concave lens for both defects.
(c) Convex and concave lens

Explanation: Hypermetropia or farsightedness can be corrected by using convex lens of appropriate power and myopia by a concave lens of appropriate power.

Question 23.
The layer of atmosphere whose temperature is less than that of the hotter layer behaves as an optically
(a) denser medium
(b) rarer medium
(c) inactive medium
(d) either denser or rarer medium
(a) denser medium

Explanation: The layer of atmosphere whose temperature is less than that of hotter layer is more denser as compared to the hotter layer of the atmosphere. So, when light travels from a cooler layer of atmosphere to a hotter Layer, it will bend away from the normal.

Question 24.
The sun appears white at noon as:
(a) Blue colour is scattered the most
(b) Red colour is scattered the most
(c) Light is least scattered
(d) All the colours of the white light are scattered away

### Assertion Reasoning questions Class 10 Science Chapter 11

For the following questions, two statements are given-one tabled Assertion (A) and the other labeled Reason (R) select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below: ,
(a) Both (A) and (R) are true and (R) is correct explanation of the (A).
(b) Both (A) and (R) are true but (R) is not correct explanation of the (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 25.
Assertion (A): Sky appears in blue colour.
Reason (R): Blue colour in sunlight travelling through atmosphere undergoes maximum scattering.
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).

Explanation: The blue colour of the sky is due to the scattering of blue colour to the maximum extent by dust particles. The blue colour appears to be coming from the sky. Blue colour has the least wavelength. Hence, the correct option is (a).

Question 26.
Assertion (A): When white light passes through a glass prism, red colour has deviated the least.
Reason (R): Red colour has the minimum speed in the glass prism.
(c) (A) is true but (R) is false.

Explanation: When white light passes through a glass prism, red colour deviates the least because red colour has maximum speed in the prism.

Question 27.
Assertion (A): When objects are observed through hot air, they appear to be moving slightly.
Reason (R): Hotter air is optically denser and the cooler air is optically rarer.

Question 28.
Assertion (A): A rainbow is always formed in the sky after a rain shower and in the same direction as the sun.
Reason (R): Water droplets act as tiny prisms.
(d) (A) is false but (R) is true.

Explanation: A rainbow is always formed in the sky in a direction opposite to that of the sun. The water droplets present in the sky act as tiny prisms, which refract and disperse sunlight, then reflect it internally and finally refract it again when it comes out of the raindrop.

Question 29.
Assertion (A): The sun’s disc appears to be flattened at sunrise and sunset.
Reason (R): The sun is near the horizon at sunrise and sunset and sunlight suffers atmospheric refraction.

(Competency Based Questions (CBQs))

Question 1.
Ankit remarked that he has seen wavering of objects when seen through a stream of hot air rising above a tandoor or a fire. He said that the air just above the fire becomes hotter than the air further higher up. He further said that this wavering can also be seen in the earth’s atmosphere as the earth’s atmosphere is not evenly distributed and several observations can be explained on the basis of this phenomenon.
(A) Name the phenomenon about which Ankit remarked.
(B) Name two observations which can be explained by the above phenomenon.
(C) What is the total time difference on duration of day on earth?
(D) Why don’t planets twinkle?
(B) The two observations are: twinkling of stars, advance sunrise, delayed sunset and apparent position of stars. (Any two).
(D) Planets are much closer to the earth and can be considered as extended sources or a collection of several point sources. The total variation in intensity of light entering our eyes from each of these point sources average out to zero, thereby nullifying the twinkling effect.

Question 2.
Renu was returning home after purchasing some medicines for her mother. It was noon and really very hot on that particular day. She tried to look at the sun but the sun was shining so brightly that she could hardly see it directly. She somehow managed to see its reflection on a window and noticed that the colour of sun was white.

At noon, the Sun appears white as:
(a) light is least scattered
(b) all the colours of the white light are scattered away
(c) blue colour is scattered the most
(d) red colour is scattered the most
(a) light is least scattered
Explanation: At noon, the sun is directly over head and has lesser air to travel through and thus will be reduced if the distance to be traveled in air is reduced. Less scattering leads to the Sun appearing white as only a little of the blue and violet colour is scattered.

Question 3.
Raman is a keen observer and loved the spectacular colours in a rainbow. He also observed the same pattern when he allowed sunlight to pass through a glass prism. He guessed that it is due to the inclined refracting surfaces of a glass prism which is responsible for showing such exciting phenomenon. Whereas, no such phenomenon was observed when light passes through a glass slab.
(A) Name the phenomenon which could explain the formation of rainbow.
The phenomenon which could explain the formation of rainbow is dispersion or splitting of light into its component colours.

(B) What is the band of colours known as?

(C) What is the cause of formation of band of colours?
The cause for formation of spectrum of light is that different colours of Light bend through different angles with respect to the incident ray as light passes through a prism,

(D) Why don’t we observe similar band of colours when light passes through a glass slab?
We don’t observe splitting of white light into its component colours when light passes through a glass slab because the refracting surfaces in a glass slab are parallel to each other whereas they are inclined at an angle in a glass prism

Question 4.
Sunny and his friends went to the terrace of their apartment building to watch the night sky. They noticed that all apartment buildings had red light installed at the terrace. Sunny had also seen red lights on top of tall towers such as the Pitampura TV tower and even on top of the GSM towers.

The danger signals installed at the top of tall buildings are red in colour, These can be easily seen from a distance because among all other colours, the red light:
(a) is scattered the most by smoke or fog
(b) is scattered the least by smoke or fog
(c) is absorbed the most by smoke or fog
(d) moves the fastest in air
(b) is scattered the Least by smoke or fog

Explanation: Among all the colours, red is scattered the Least by smoke or fog. This is because the wavelength of red colour is the largest. Thus, it can be easily seen from a distance. Since the wavelength of red light is maximum in the spectrum, it’s penetration power in the air is maximum and so we can see red colour from farther distances, thus, danger signal uses red colour.

Question 5.
Fix a sheet of white paper on a drawing board using drawing pins. Place a glass prism on it in such a way that it rests on its triangular base. Trace the outline of the prism using a pencil. Draw a straight line PE inclined to one of the refracting surfaces, say AB, of the prism. Fix two pins, say at points P and Q, on the line PE as shown in Fig. below.

Look for the images of the pins, fixed at P and Q, through the other face AC. Fix two more pins, at points R and S, such that the pins at R. and S and the images of the pins at P and Q lie on the same straight line. Remove the pins and the glass prism. The line PE meets the boundary of the prism at point E. Similarly, join and produce the points R and S. Let these lines meet the boundary of the prism at E and F, respectively. Join E and F. Draw perpendiculars to the refracting surfaces AB and AC of the prism at points E and F, respectively. Mark the angle of incidence (i), the angle of refraction (r) and the angle of emergence (e) as shown in Fig.

(A) Given below are four statements regarding incident ray, refracted ray and emergent ray in the above figure.
Select the incorrect statements:
(I) PE is the incident ray.
(II) EF is the emergent ray.
(III) EF is the refracted ray and FS is the emergent ray.
(IV)PE is the incident ray and FS is the refracted ray.
(a) Both (1) and (II)
(b) Both (I) and (III)
(c) Both (II) and (IV)
(d) Both (III) and (IV)
(c) Both (II) and (IV)

Explanation: Here PE is the incident ray, EF is the refracted ray and FS is the emergent ray. PE is the incident ray as light, is incident on the prism face AB. Light undergoes refraction in the glass prism and bends away from the normal and hence EF is the refracted ray. The ray FS is the emergent ray as light emerges out of the face AC of the prism along this direction.

(B) The angles of incidence (i), refraction (r) and emergence (e) are mentioned in the table below. Select the row containing the correct marking of angles:

(C) The angle of deviation is the angle between:
(a) Refracted ray and incident ray
(b) Refracted ray and emergent ray
(c) Emergent ray and face AC of the prism
(d) Emergent ray and incident ray

(D) In a glass prism, the emergent ray is not parallel to the incident ray as:
(a) The laws of refraction do not hold in the case of glass prism.
(b) The refracting surfaces are inclined at an angle.
(c) The angle of refraction in glass is greater than the angle of incidence.
(d) The angle of refraction in glass is greater than the angle of emergence.

(E) If n is the refractive index of glass of which the prism is made, which of the following relations is correct ?
(a) n = $$\frac{\sin \angle i}{\sin \angle r}$$
(b) n = $$\frac{\sin \angle r}{\sin \angle i}$$
(c) n = $$\frac{\sin 90^{\circ}}{\sin \angle e}$$
(d) n = $$\frac{\sin \angle r}{\sin \angle e}$$
(a) n = $$\frac{\sin \angle i}{\sin \angle r}$$

Question 6.
While walking along the beach in Mumbai, Madhuri and her friends were amazed at the beauty of the setting sun and its reflection on the sea against the backdrop of buildings. They observed that the sun appeared reddish at sunset and even at sunrise.

Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?
(a) Dispersion of light
(b) Scattering of light
(c) Total internal reflection of light
(d) Reflection of light from Earth
(b) Scattering of light

Explanation: Scattering of light contributes to the reddish appearance of the Sun at sunrise or sunset. Near the horizon, most of the blue light and shorter wavelengths are scattered away by the particles. Therefore, the light that reaches our eyes is of longer wavelengths. The red light has the maximum wavelength. This gives rise to the reddish appearance of the Sun.

Related Theory
Light from the Sun, near the horizon, passes through thicker layers of air and a large distance in Earth’s atmosphere before reaching our eyes. Near the horizon, most of the blue light and shorter wavelengths are scattered awau by the particles. Therefore, the light that reaches our eyes is of longer wavelengths. The red light has the maximum wavelength. This gives rise to the reddish appearance of the Sun.

Question 7.
Place a strong source (S) of white light at the focus of a converging lens (Lj). Allow the light beam to pass through a transparent glass tank (T) containing clear water. Allow the beam of light to pass through a circular hole (c) made in a cardboard. Obtain a sharp image of the circular hole on a screen (MN) using a second converging lens (Ly), as shown in Fig. below.
Dissolve about 200 g of sodium thiosulphate (hypo) in about 2 L of clean water taken in the tank. Add about 1 to 2 mi of concentrated sulphuric acid to the water.

(A) What is the role of lenses L1 and L2 in the activity?

 Role of Lens L1 Role of Lens L2 (a) Converges a beam of light placed at S Converges a parallel beam of light (b) Provides a parallel beam of light Converges a parallel beam of light (c) Provides a parallel beam of light Provides a parallel beam of light (d) Converges a beam of light placed at S Provides a parallel beam of light

(B) When about 200 g of sodium thiosulphate (hypo) is dissolved in about 2 L of clean water taken in the tank and about 1 to 2 mL of concentrated sulphuric acid is added to the water, it is observed that:
(a) A true solution is formed after 2 to 3 minutes.
(b) A suspension of sodium is formed in the tank
(c) Sulphur particles start precipitating in about 2 to 3 minutes.
(d) No change is observed.
(c) Sulphur particles start precipitating in about 2 to 3 minutes.

Explanation: We will find fine microscopic sulphur particles precipitating in about 2 to 3 minutes due to the reaction between sulphuric acid and sodium thiosulphate.

(C) The observations regarding change in colour of light in the tank about 2 to 3 minutes after adding sulphuric acid to hypo is:
(I) Blue light can be seen from the side of the tank facing the circular hole.
(II) Blue light can be seen from the three sides of the glass tank.
(III) At first orange-red light and then red light can be seen from the side of the tank facing the circular hole.
(IV) At first orange-red light and then red light can be seen from the three sides of the glass tank.
Select the incorrect observations:
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)

(D) The observations can be explained by the phenomenon of:
(a) Scattering of light
(b) Reflection of light
(c) Refraction of light
(d) Dispersion of light

(E) The activity above helps us in understanding:
(a) Twinkling of stars
(b) Formation of rainbow
(c) Advance sunrise and delayed sunset
(d) Reddish appearance of the Sun at the sunrise
(d) Reddish appearance of the Sun at the sunrise

Explanation: This activity demonstrates the scattering of light that helps us to understand the bluish colour of the sky and the reddish appearance of the Sun at the sunrise or the sunset. Near the horizon, most of the blue light and shorter wavelengths are scattered away by the particles. Therefore, the light that reaches our eyes is of longer wavelengths. This gives rise to the reddish appearance of the Sun.

Question 8.
Parth noticed that his father had two sets of spectacles. So he asked him the reason for the same. His father explained that one spectacle is for viewing distant objects while the other is for reading books. It means that his father had both the defects of vision- farsightedness as well as nearsightedness.

The defect of vision in which the image of nearby objects is formed behind the retina is
(a) Near sightedness
(b) Cataract
(c) Far sightedness
(d) Presbyopia
(c) Far sightedness

Explanation: Farsightedness or hypermetropia is the defect of vision in which the image of a nearby object is formed behind the retina due to either long focal length of the eye lens or shortening of the eye ball.

Question 9.
We’ve all seen that part in the movie where the weary desert wanderer has been walking for hours and is dying of thirst. Then he happens upon a vast body of water on the horizon. He runs towards the water, it grows closer and closer, until he springs himself into the air only to land back down in the sand and no water in sight. Well, that is due to an optical illusion called Mirage.

Mirage is an optical phenomenon which creates an illusion of the presence of water and is a result of refraction of light from a non-uniform medium. Mirage is observed mainly during sunny days when driving on a roadway. Normally, light waves from the sun travel straight through the atmosphere to your eye. But, light travels at different speeds through hot air and cold air.

Mirages happen when the ground is very hot and the air is cool and a ray of light gets refracted more and more away from the normal. At a particular angle when a ray of light exceeds critical angle, total internal reflection takes place and ray of light gets reflected in the same medium. When the reflected ray reaches our eye, it appears as coming from tree or sky and hence the inverted image of tree creates an impression from a pond of water.

(A) Mirage is an example of:
(a) Reflection of tight and Refraction of Light
(b) Dispersion of Light
(c) Total internat Reflection
(d) Refraction of Ught and Total internal Reflection of Light
(d) Refraction of light and Total Internal Reflection of Light

Explanation: As the air just above the ground is hotter than the air above it, light traveling from a distant object travels from a denser medium to a rarer medium and hence bends away from the normal. So, it undergoes refraction. Since light is travelling from a denser medium to a rarer medium, at a certain angle which is greater than the critical angle, the light undergoes total internal reflection.

(B) Mirages are more common in:
(a) rainforests
(b) dry forests
(c) deserts
(d) highlands
(c) deserts

Explanation: Mirages are formed on hot sunny days in deserts or road surfaces when the air just above the ground is much hotter than the air above it.

(C) Mirage is formed because:
(I) Air above the ground is very hot and air above is cooler
(II) Air above the ground is cooL and air above is warmer.
(III) Light rays from a distant object bend towards the normal when coming towards the ground.
(IV) Light rays from a distant object bend away from the normal when coming towards the ground.
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (II) and (IV)
(b) Both (I) and (IV)

Explanation: Mirage is formed on a hot day when the air just above the ground is hotter than the air above it. As hotter air is optically rarer than cooler air, light traveling from a distant object travels from a denser medium to a rarer medium and hence bends away from the normal. Since light is travelling from a denser medium to a rarer medium, at a certain angle which is greater than the critical angle, the light undergoes total internal reflection.

(D) Atmospheric refraction occurs because:
(a) Refractive index in medium is gradually changing
(b) Of presence of dust particles in atmosphere
(c) Large amount of moisture is present in atmosphere on a humid day
(d) Sun’s rays travel the most when sun is near the horizon

(E) When starlight enters the earth’s atmosphere:
(a) it bends away from the normal
(b) It bends towards the normal
(c) It first bends towards the normal and then away from the normal
(d) It first bends away from the normal and then towards the normal.

Question 10.
The rising sun looks so beautiful! On a trip to a hill station, Raj was overjoyed to see such a beautiful sight of the sun just rising above the horizon! But his father later told him that the sun had not risen yet and what he is actually seeing is due to an optical phenomenon!

Why is the sun visible to us 2 minutes before actual sunrise and 2 minutes after actual sunset?

The sun is visible to us 2 minutes before actual sunrise and 2 minutes after actual sunset due to the phenomenon of atmospheric refraction. During this time when the sun is still below the horizon, the sun’s rays enter the earth’s atmosphere and undergo continuous refraction and bend towards the normal as the refractive index increases continuously as we reach the earth’s surface. So. the sun is visible to us.

Question 11.
The inner workings of the human eye are corn ple but at the same time, fascinating. Have you wondered how exactly they do work or what are the major parts of the eye involved in creating Vision? It helps us in visualizing objects and also helps us in light perception, color, and depth perception. Besides, these sense organs are pretty much similar to cameras, and they help us see objects when light coming from outside enters into them. The structures and functions of the eyes are complex. Each eye constantly adjusts the amount of light it lets in, focuses on objects near and far, and produces continuous images that are instantly transmitted to the brain.

(A) The image formed by eye tens ¡s:
(a) Real and erect
(b) Virtual and erect
(c) Real and inverted
(d) Virtual and inverted
(c) Real and inverted

Explanation: The eye Lens forms an inverted and real image of the object on the retina as eye tens is a convex lens.

(B) Most of the refraction for the light rays entering the eye occurs at:
(a) Outer surface of the cornea.
(b) Eye Lens
(c) Pupil
(d) Vitreous humour
(a) Outer surface of the cornea.

Explanation: Most of the refraction for the Light rays entering the eye occurs at the Outer surface of the cornea. The crystalline Lens mereLy provides the finer adjustment of focal length required to focus objects at different distances on the retina.

(C) Select the correct statements:
(I) The change in the curvature of the eye lens can change its focal length.
(II) When the citiary muscles are relaxed, the Lens becomes thin and its focal length decreases.
(III) When the ciliary muscles contract, the Lens becomes thicker and its focal length increases.
(IV)Thin tens enables us to view distant objects clearly whereas thick lens enables us to see nearby objects clearly.
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (II) and (IV)

(D) The near point and far point of a young adult with normal vision is:
(a) Near point = 0 cm and Far point = 25cm
(b) Near point = 25 cm and far point = 50 m
(c) Near point = 0 m and far point = infinity
(d) Near point = 25 cm and far point = infinity

(E) Select the row containing incorrect part of human eye and its function

 Part of Human Eye Function (a) Retina Delicate membrane having Large number of Light-sensitive cells. (b) Iris Changes the curvature of eye Lens (c) Cornea A thin membrane through which Light enters the eye (d) Pupil An aperture that regukites and controls the amount of Light

(b) Part of Human Eye: Iris; Function: Change the curvature of eye Lens.

Explanation: Iris is a dark muscular assembly that controls the size of the pupil. The muscle that changes the curvature of eye lens is ciliary muscles.

Question 12.
Shradhas parents took her grandfather to the eye speciaList as he was complaining of difficulty in seeing things. The doctor diagnosed it as cataract and said that it is quite common in old age.

What is cataract? How is it caused? How can it be corrected?
The condition when there is partial or complete loss of vision in the eye of people at old age is known as cataract. It is caused when the crystalline lens of eye becomes milky andcloudy.

It can be corrected through a cataract surgery.

Question 13.
Piyush, who was a backbencher in class, started complaining of frequent headaches. His parents took him to the nearest clinic and the doctor referred him to the eye specialist. The eye specialist tested his vision and asked Piyush whether he was able to read whatever the teacher wrote on the blackboard clearly or not. He replied in the negative. The doctor told his parents about the defect of vision that Piyush was suffering from and advised corrective glasses.
After wearing the glasses, Piyush was now able to read the black board clearly and also got rid of his headaches.

(A) @Piyush was suffering from:
(a) Cataract
(b) Myopia
(c) Hypermetropic
(d) Presbyopia

(B) Select the correct statements regarding the defect of vision Piyush was suffering from:
(I) A person with this defect has the far point nearer than infinity.
(II) A person with this defect has the near point greater than the least distance of distinct vision.
(III) A person suffering from this defect may see clearly upto a distance of a few metres.
(IV) A person suffering from this defect may not see clearly beyond the near point.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
(a) Both (I) and (III)

Explanation: As Piyush is suffering from myopia, a person with this defect has the far point nearer than infinity. A person suffering from this defect may see clearly upto a distance of a few metres. That is why myopia is also known as short sightedness.

(C) Which of the following is not true about the defect of vision Piyush is suffering from ?
(a) It is caused due to excessive curvature of the eye lens
(b) It may be caused due to elongation of the eyeball.
(c) The image of a distant object is formed behind the retina.
(d) It is corrected by using a concave lens of appropriate power.

(D) The far point of a myopic person is 50 cm in front of the eyes. The nature and power of the lens required for correct the problem is:

 Nature of Lens Power of Lens (a) Concave – 0.5 D (b) Concave – 2.0 D (c) Convex + 0.5D (d) Convex + 2.0D

(b) Nature of Lens – Concave: Power of Lens – 2.0 D

Explanation: To find the focal length, we use the lens formula
$$\frac{1}{f}=\frac{1}{v}-\frac{1}{u} \Rightarrow \frac{1}{f}=-\frac{1}{50}$$ ⇒ f = – 0.5 m
Power of the lens = $$-\frac{1}{0.5}$$ = – 2.0 D
As focal length of the corrective lens is negative, the type of lens used is a concave lens.

(E) A person needs a lens of power – 4.5 D for correction of her vision. The nature of lens and its focal length is:

 Nature of Lens Focal length (a) Concave – 45cm (b) Convex – 45cm (c) Convex + 22.22 cm (d) Concave + 22.22 cm

(d) Nature of Lens – Concave :Focal Length – 22.22 cm

Explanation: It is given that the power of the corrective lens = – 4.5 D. We know that
As the focal length is negative, the lens is a concave lens.

Question 14.
Pankaj noticed that while reading books or newspaper, most people keep the book neither too far nor too close to their eyes. So, he himseLf tried to find out what happens when he tried to read the book by keeping the book quite far. He immediately said that he could not read all Letters clearly. When he tried to read a book by keeping it very dose to his eyes, the letters had become blurred and his eyes started paining!

Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
The normal eye has the remarkable property to see objects when placed at any distance from the eye due to the ability of the eye lens to adjust its focal length which is called accommodation. However, the normal eye is not able to see clearly objects placed closer to 25 cmas the focal length of the eye lens cannot bedecreased below a certain minimum limit.

Question 15.
Everyone enjoys the spectacle of a rainbow glimmering against a dark stormy sky. How does sunlight falling on clear drops of rain get broken into the rainbow of colors we see? The same process causes white light to be broken into colors by a clear glass prism or a diamond. Sunlight, considered to be white, actually appears to be a bit yellow because of its mixture of wavelengths, but it does contain all visible wavelengths.
The sequence of colors in rainbows is the same sequence as the colors plotted versus wavelength in Figure below. What this implies is that white light is spread out according to wavelength in a rainbow.
(A) The phenomena that play a role in the formation of rainbow is:
(a) Reflection and refraction of light
(b) Refraction, absorption, dispersion and refraction of light
(c) Dispersion, refraction and reflection of light
(d) Refraction, dispersion, reflection and refraction of light
(d) Refraction, dispersion, reflection and refraction of light

Explanation: Rainbow is produced after the rain, by refraction, dispersion, total internal reflection and again refraction process in droplets of water

(B) Select the colours in the correct ascending of wavelength:
(a) Blue, Green, Red
(b) Orange, Green, Red
(c) Blue, Yellow, Green
(d) Orange, Yellow, Green

(C) Select the incorrect statements about rainbow:
(I) Rainbow is caused by scattering of sunlight by tiny water droplets, present in the atmosphere.
(II) A rainbow is always formed in a direction opposite to that of the Sun.
(III) The water droplets refract and scatter the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop.
(IV) Different colours reach the observer’s eye due to the scattering of light and internal reflection.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (III) and (IV)
(d) (II), (III) and (IV)
(c) (I), (III) and (IV)

Explanation: A rainbow is a natural spectrum appearing in the sky after a rain shower, it is caused by dispersion of sunlight by tiny water droplets, present in the atmosphere which act like small prisms. A rainbow is always formed in a direction opposite to that of the Sun. The tiny droplets of water refract and disperse the incident sunlight, then reflect it internally, and finally refract the light again when it comes out of the raindrop. Due to the dispersion of light and internal reflection, different colours reach the observer’s eye.

(D) A spectrum of light is observed when white light is directed to a prism as:
(a) The different colours in the white light bend away from the normal line at different angles on entering prism.
(b) The different colours in the white
light bend towards the normal line at different angles on entering prism.
(c) The different colours in the white light bend away from the normal at same speed to each other on entering prism.
(d) The different colours in the white light bend towards the normal at same speed to each other on entering prism.

(E) The velocity of waves of all colours is same in:
(a) Water
(b) Oxygen
(c) Vacuum
(d) Glass

Question 16.
Mike and his friends were enjoying a bonfire in their garden. One of his friends noticed that the air above the fire was wavering. He realized that this is because the physical conditions of air are notstationary because of which the apparent position of the object, as seen through the hotair, changes continuously. This phenomenon can also be used to explain several observations around us.

Why do stars appear higher than they actually are?
Stars appear higher than they actually are due to the phenomenon of atmospheric refraction. When the starlight enters the earth’s atmosphere, it undergoes refraction continuously before it reaches the earth as the refractive index of the atmosphere changes continuously. The atmosphere bendsstarlight towards the normal due to which the apparent position of thestar is slightly different from its actual position.

Question 17.
In addition to being absorbed or transmitted, electromagnetic radiation can also be reflected or scattered by particles in the atmosphere. Scattering is the redirection of electromagnetic energy by suspended particles in the atmosphere. The Tyndall effect is light scattering by particles in a colloid or in a very fine suspension.

The type and amount of scattering that occurs depends on the size of the particles and the wavelength of the energy. Rayleigh scatter occurs when radiation (light) interacts with molecules and particles in the atmosphere that are smaller in diameter than the wavelength of the incoming radiation. Shorter wavelengths are more readily scattered tha longer wavelengths.

(A) Which of the following will not show Tyndall effect?
(a) Milk
(b) Sugar solution
(c) Smoke
(d) Emulsion
(b) Sugar solution

Explanation: Tyndall effect is shown by colloids and suspensions but not shown by true solutions. As sugar solution is a true solution, it will not show Tyndall effect.

(B) Tyndall effect is due to
(a) Refraction of light
(b) Dispersion of light
(c) Absorption of light
(d) Scattering of light
(d) Scattering of light

Explanation: Tyndall effect is due to scattering of light by particles present in the atmosphere, such as smoke, fine dust particles and gas molecules.

(C) Which of the following natural phenomena are not due to scattering of light in nature?
(I) Blue colour of sky
(II) Twinkling of stars
(III) Formation of rainbow
(IV) Colour of water in deep sea
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (II) and (IV)
(d) Both (III) and (IV)

(D) The table below lists the colour of scattered light for different sizes of scattering particles.
Select the row containing the correct information:

(E) The blue colour of the sky is because:
(a) Red colour is scattered more as compared to other colours
(b) Red colour is absorbed more as compared to other colours
(c) Blue colour is scattered more as compared to other colours
(d) Blue colour is absorbed more as compared to other colours
(c) Blue colour is scattered more as compared to other colours

Explanation: The molecules of air and other fine particles in the atmosphere have sizesmaller than the wavelength of visible light and these are more effective inscattering Light of shorter wavelengths at the blue end than light of longerwa wavelengths at the red end. Thus, when sunlight passes through the atmosphere, the fine particles in air scatter the blue colour (shorter wavelengths) more strongly than red and the sky appears blue to us as the scattered blue light entersour eyes.

Question 1.
What would have been the colour of sky if the earth had no atmosphere?

Question 2.
Why do stars appear higher than their actual position?
Stars appear higher than their actual position as starlight undergoes refraction continuously on entering earth’s atmosphere and bends towards the normal.

Question 3.
On the basis of which observation did Newton conclude that sunlight is made up of seven colours?

Question 4.
How does the refractive index of earth’s atmosphere vary with height?

Question 5.
Why is a small amount of sodium thiosulphate added to water in tank in the activity to understand reddish appearance of sun at sunrise and sunset?
Sodium thiosulphate is added to water in the tank for precipitating minute colloidal sulphur particles which scatter short wavelengths of Light.

Question 6.
State one effect produced by the scattering of light by the atmosphere?
There are two effects produced due to scattering of light in the atmosphere: Tyndall effect and appearance of the blue colour of the sky.

Related Theory
When light moves from one medium to another, the light scatters in different directions due to change in the medium. This is called scattering of light. When tiny particles of dust come in front of light and leads to its scattering, this is called Tyndall effect. We can see these tiny dust particles in the scattered light.

When the light from stars enters the atmosphere, the light with smaller wavelengths gets easily scattered, while lights with longer wavelength do not scatter much and hence travels straight. This gives red colour to the sky during sunrise and sunset.

On the other hand, the shorter wavelengths scatter in the sky and give the sky its usual blue colour.

Question 7.
An astronaut in space finds sky to be dark. Explain reason for this observation. [Diksha]

Question 8.
What is a rainbow? Draw a labelled diagram to show the formation of a rainbow.
Rainbow: A rainbow is a natural spectrum formed in the sky after a rain shower due to the dispersion of sunlight by the tiny droplets of water present in the atmosphere. The tiny droplets of water act like small prisms which refract and disperse the incident sunlight, then reflect the light internally and finally refract it again when it comes out of the raindrop. Different colours reach the observer’s eyes due to the dispersion of light and internal reflection.

Question 9.
Why does the sun appear white at noon?

## Online Education MCQ Questions for Class 10 Science Chapter 12 Electricity with Answers

Students can also read Online Education MCQ Questions for Class 10 Science Chapter 12 Electricity Questions with Answers hope will definitely help for your board exams. https://ncertmcq.com/mcq-questions-for-class-10-science-with-answers/

## Online Education for Electricity Class 10 MCQs Questions with Answers

Electricity Class 10 MCQ Question 1.
The values of mA and µA are:
(a) 10-6 and 10-9 A respectively
(b) 10-3 and 10-6 A respectively
(c) 10-3 and 10-9 A respectively
(d) 10-6 and 10-3 A respectively
(b) 10-3 A and 10-6 A.

Explanation: An ampere is the SI unit of electric current
1A = 1000mA Or 1mA = $$\frac{1 \mathrm{~A}}{1000}$$ = 103A

∴ 1 µA = 10-3 × 10-3 A = 10-6A

Electricity MCQ Class 10 Question 2.
A cylindrical conductor of Length ‘l’ and uniform area of cross-section ‘A’ has resistance ‘R’. Another conductor of Length 2.5 1 and resistance 0.5 R of the same material has area of cross-section.
(a) 5A
(b) 2.5A
(c) 0.5A
(d) $$\frac{1}{5}$$ A

Class 10 Electricity MCQ Question 3.
Identify the circuit in which the electrical components have been properly connected.

(a) (I)
(b) (II)
(c) (III)
(d) (IV)
(b) (II)

Explanation: In figure (I), the voltmeter is connected in series (not parallel). Similarly, in figure (III). the ammeter ¡s in parallel which should be in series. In figure (IV), the negative terminal of battery has been connected to the positive terminal of the ammeter, whereas it should be connected to the negative terminal

Related Theory:
Essential conditions when components connected:

• The voltmeter should be connected in parallel
• The ammeter should be connected in series.
• Positive terminals of the voltmeter arid ammeter should be connected to the positive terminal of the cell and their negative removals should be joined to the negative terminal of the cell

Electricity Class 10 MCQ With Answers Question 4.
If a person has five resistors each of value Ω, then the maximum resistance he can obtain by connecting them ¡s:
(a)1 Ω
(b)5 Ω
(c) 10 Ω
(d) 25 Ω

MCQ On Electricity Class 10 Question 5.
What is the minimum resistance which can be made using five resistors, each of $$\frac{1}{5}$$ Ω?
(a) $$\frac{1}{5}$$ Ω
(b) $$\frac{1}{25}$$ Ω
(c) $$\frac{1}{10}$$ Ω
(d) 25 Ω

Class 10 Science Chapter 12 MCQ Question 6.
The resistance of a resistor is reduced to half of its initial value. In doing so, if other parameters of the circuit remain unchanged, the heating effects in the resistor will become:
(a) two times
(b) half
(c) one-fourth
(d) four times
(a) two times

Explanation: Resistance of a resistor R Q New resistance of a resistor Q

All other parameters of the circuit remain unchanged

By applying Joule’s law of heating H = I2Rt

As per Ohms Law V = IR Or I = $$\frac{V}{R}$$

Hence, the heating effect in the resistor will become two times if all other parameter of the circuit remain same.

Class 10 Science Chapter 12 MCQ With Answers Question 7.
At the time of short circuit, the electric current in the circuit:
(a) vary continuously
(b) does not change
(c) reduces substantially
(d) increases heavily

MCQ Electricity Class 10 Question 8.
Two bulbs of 100 Ω and 40 Ω are connected in series. The current through the 100 Ω bulb is 1 A. The current through the 40 Ω bulb will be:
(a) 0.4 A
(b) 0.6 A
(c) 0.8 A
(d) 1A
(d) 1 A

Explanation:

In a series combination of resistors (bulbs) the current is the same in every part of the circuit as current does not change in series combination so both the bulbs get equal amount of current Hence the current through the 40 Ωbulb will be 1A.

Ch 12 Science Class 10 MCQ Question 9.
When a 4 V battery is connected across an unknown resistor there is a current of 100 mA in the circuit. The value of the resistance of the resistor is:
(a) 4 Ω
(b) 40 Ω
(c) 400 Ω
(d) 0.4 Ω
(b) 40 Ω
V = IR, V = 4 V,
I = 100 mA = 0.1 A
Hence R = $$\frac{V}{1}=\frac{4}{0.1}$$ Ω = 40 Ω.

Class 10 Science Ch 12 MCQ Question 10.
The equivalent resistance of a series combination of two resistances is X Ohm. If the resistance are of 10 Ohm and 40 Ohm respectively, the value of X will be:
(a) 10 Ohm
(b) 20 Ohm
(c) 50 Ohm
(d) 40 Ohm [Diksha]

Class 10 Physics Electricity MCQ Question 11.
Unit of electric power may also be expressed as:
(a) volt-ampere
(b) kilowatt-hour
(c) watt-second
(d) joule-second

Class 10 Electricity MCQ Questions Question 12.
if the resistance of a certain copper wire is 1 Ω, then the resistance of a similar nichrome wire will be about:
(a) 25 Ω
(b) 30 Ω
(c) 60 Ω
(d) 45 Ω
(c) 60 Ω

Explanation: if the resistance of a certain copper wire is 1 Ω, the resistance of a similar nichrome wire will be about 60 Ω because the resistivity of nichrome is 60 times the resistivity of copper.

Electricity Class 10 MCQ Learn Cbse Question 13.
The resistivity of a certain material is 0.6 Ω m, The material is most likely to be:
(a) an insulator
(b) a superconductor
(c) a conductor
(d) a semiconductor

MCQs On Electricity Class 10 Question 14.
A cell, a resistor, a key, and an ammeter are arranged as shown in the circuit diagrams of the figure. The current recorded in the ammeter will be:

(a) Maximum in (I)
(b) Maximum in (II)
(c) Maximum in (III)
(d) The same in all the cases
(d) The same in all the cases

Explanation: In series connections, the order of elements in the circuit will not affect the amount of current flowing in the circuit.

Class 10 Science Electricity MCQ Question 15.
The instrument used for measuring electric current is:
(a) galvanometer
(b) ammeter
(c) voltmeter
(d) potentiometer

MCQs Of Electricity Class 10 Question 16.
A student plots V-l graphs for three samples of nichrome wire with resistances R1, R2 and R3. Choose from the following the statement that holds true for this graph.

(a) R1 = R2 = R3
(b) R1 > R2 > R3
(c) R3 > R2 > R1
(d) R2 > R1 > R3
(d) R2 > R1 > R3

Explanation: As is clear from the graph, the current for A2 conductor is less than A1 and A1 is Less than A3. We can say IA2 < IA1 < IA3
R2 > R1 > R3 (AS, R = V)

Chapter 12 Class 10 Science MCQ Question 17.
The maximum resistance which can be made using four resistors each of resistance $$\frac{1}{2}$$ Ω is:
(a) 2 Ω
(b) 1 Ω
(c) 2.5 Ω
(d) 8 Ω
(a) 2 Ω

Explanation: When a number of resistances are connected in series the resultant resistance is equal to the sum of the individual resistances and is greater than any individual resistance. Four resistors are given:

Hence, the maximum resistance which can be made using four resistors each of resistance $$\frac{1}{2}$$ Ω is 2 Ω.

Electricity Class 10 MCQs Question 18.
A current of 2 A is drawn by a conductor on applying a potential difference of 6 V across its ends. The number of electrons passing through a cross-section of the conductor and the heat generated in the conductor in 8 seconds is:

 Number of Electrons Passing in 8 s Heat Generated in 8 s (a) 1.6 × 10-20 24J (b) 1020 96J (c) 1.28 × 10-18 3.6 × 106J (d) 1030 96J

Class 10th Science Chapter 12 MCQ Question 19.
The resistivity of four wires A, B, C, and D are of the order of 1012, 10-6, 10-8, and 1014 respectively. !f the wires are of equal lengths and equal areas of cross-section, then select the row containing the correct information:

 Resistance Nature (a) Resistance of C will be the least C is the conductor best of electricity (b) Resistance of A will be the largest A is a good conductor of electricity (c) Resistance of B will be the largest B is a poor conductor of electricity (d) Resistance of D will be the least D is the conductor best of electricity

Question 20.
Given below are four statements on resistance of a conductor. Select the incorrect statements:
(I) If in an electric circuit, the resistance is doubled the voltage also gets doubled.
(II) If in an electric circuit, the resistance is halved the current gets doubled.
(III) Variable resistance is a component used to regulate voltage without changing the current.
(b) Both (I) and (III)

Explanation: According to Ohm’s law, V = IR.
Therefore, l = $$\frac{V}{R}$$.

It means that if resistance R is doubled, the current gets halved, but the voltage remains the same. Similarly, if resistance is halved, currently gets doubled.

Question 21.
Given below are four statements about resistivity. Select the incorrect statements:
(I) Resistivity is a characteristic property of the material and varies with temperature.
(II) Resistivity depends on the length and area of the cross-section of the conductor.
(III) Metals and alloys have very low resistivity and are good conductors of electricity.
(IV) Insulators have low resistivity of the order of 1012 to 1017 Ohm.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) Both (II) and (iV)

Question 22.
Select the correct statements from the statements given below:
(I) In a parallel circuit the current is constant throughout the electric circuit.
(II) In a parallel circuit the other components keep working even if one component fails.
(III) In a series circuit when one component fails, the circuit is broken and the other components stop working.
(IV) in a series circuit, the current is divided among the electrical gadgets depending upon their resistance.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) (I), (III), and (IV)
(b) Both (II) and (III)

Explanation: In a series circuit, the current is constant through the electric circuit and if one component fails, the other components also stop working. Whereas in a parallel circuit, the current is divided among the different components depending upon their resistance, and if one component fails, the other components keep working.

Question 23.
The unit of potential difference is:
(a) JC
(b) J/C
(c) J
(d) C/J
(b)J/C

Explanation: Potential difference between two points in an electric field of a given charge is defined as the work done in moving a unit positive charge from one point to another. As V = $$\frac{W}{q}$$ , the unit of potential difference is Joule/ Coulomb or J/C.

Question 24.
If both the length of a conductor and its radius is doubled, the ratio of new resistance and original resistance will be:
(a) 1:1
(b) 2:1
(c) 4:1
(d) 1: 2

Question 25.
When a 2 Ω resistor is connected across the terminals of a 6 V battery, the charge (in coulombs) passing through the resistor per second is:
(a) 0.5
(b) 2
(c) 3
(d) 4
(c) 3

Explanation: The charge passing through a resistor per second is the same as the current passing through the resistor since current is defined as the rate of flow of charges. The current flowing is found by using Ohm’s law, V = IR. Therefore, I = V/R = 6/2 = 3A, which is the same as the charge passing in one second.

Question 26.
A battery of 6V is connected in series with resistors of 0.1 ohms, 0.2 ohms, 0.3 ohms, 0.4 ohms, and 2 ohms. How much current would flow through the 0.3-ohm resistor?
(a) 0.895A
(b) 1.2 A
(c) 2 A
(d) 3 A

### Assertion Reasoning questions Class 10 Science Chapter 12

For the following questions, two statements are given – One labeled Assertion (A) and the other labeled Reason (R), select the correct answer to these questions from the codes (a), (b), (c), and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of the (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

Question 27.
Assertion (A): At high temperatures, metal wires have a greater chance of short-circuiting.
Reason (R): Both resistance and resistivity of a material vary with temperature.
(b) Both (A) and (R) are true but (R) is not the correct explanation of the (A).

Explanation: At high temperatures, the free electrons start moving at a greater speed and more heat is evolved. The increased amount of heat melt the insulation of wires and wires have a greater chance of short-circuiting. Sometimes the short circuit may even melt the wire and it may cause fire.

Both resistance and resistivity vary with temperature. When the temperature is increased, the random motion of electrons increases. As a result the number of collisions increases between atoms and electrons.

Question 28.
Assertion (A): When two ends of a metallic wire are connected across the terminals of a cell, then some potential difference is set up between its ends. The direction of electrons are from a positive terminal to negative terminal of the cell.
Reason (R): Electrons are flowing through the conductors from its higher potential to its lower potential end. [Diksha]

Question 29.
Assertion: A fuse wire is always connected in parallel with the mainline.
Reason: If a current larger than the specified value flows through the circuit, fuse wire melts.

Question 30.
Assertion(A): Electric appliances with the metallic body have three pin connection, whereas an electric bulb has a two pin connection.
Reason (R): Three pin connection reduce heating of connecting wires. [Diksha]
(c) (A) is true but (R) is false.

Explanation: The three connection of electric appliances with metallic body are live wire, neutraL wire and earth wire. The live and neutraL wire supply electric current to the appliance, whereas the earth wire, which is connected to the metal body of the electric appliance, protects us from electric shock in case we touch the metal body of appliances.

In case of an electric shock, the current passes directly to the earth through the earth wire and we do not feel the electric shock.

On the contrary, three-pin connection do not reduce heating of connecting wires.

Question 31.
Assertion (A): In a purely resistive circuit, the source energy is dissipated in the form of heat.
Reason (R): The potential difference across the ends of a conductor is directly proportional to the current flowing through it.

Question 32.
Assertion (A): Alloys are commonly used in electrical heating devices like electric ion and heater.
Reason (R): Resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points then their constituents, metals.
(a) Both (A) and (R) are true and (R) is correct explanation of the assertion.

Related Theory
Alloys have more resistivity than of its constituent elements because alloys have better properties than that of metals. Resistivity is the property of a material that explains how strongly the material opposes flow of electrons. Higher the resistivity, smaller will be the conductivity i.e. why alloys are used in electrical heating devices.

Metals have a higher melting point as the atoms are arranged in a regular manner and form a strong bond whereas alloys are made up of different metals. The different sizes of atoms in an alloy make their arrangement less regular than a pure metal. This makes the bonds between the atoms weaker and lowers the melting point.

(Competency Based Questions (CBQs))

Question 1.
The following table given below shows the resistivity of three materials X. Y and Z Analyse the table and answer the following questions:

(A) Arrange the samples in increasing order of conductivity.
Conductivity is inversely proportional to resistivity so Y < X < Z.

(B) Which of these is the best conductor?
Z is the best insulator as it has the least resistivity.

(C) Which are these is the best insulators?
(a) X
(b)Y
(c) Z
(d) None of these

(D) Electrical resistivity of a given metallic wire depends upon:
(a) Its length
(b) Its thickness
(c) Its shape
(d) Nature of the material
(d) Nature of the material

Explanation: The resistivity of a material depends on the nature and the temperature of the conductor, but not its shape and size.

Question 2.
Shivani 8 had studied in her class that an electric bulb consists of a filament made up of a metal having high melting point such as tungsten. Also, the bulbs are filled with a chemically inert gas such as nitrogen or argon to prolong the life of filament.

A current of 1 A is drawn by a filament of anelectric bulb. The number of electrons passingthrough a cross-section of the filament in 16seconds would be roughly:
(a) 1020
(b) 1016
(c) 1018
(d) 1023
(a) 1020
Explanation: Electric current, 1 = 1 A Time, t = 16 seconds No. of electrons, n = ?

We know that current is the amount of electric charge passing through a given point of conductor in 1 second.

The number of eectrons flowing is 1020 electrons.

Question 3.
The following table given below shows the information about two heaters A and B. Analyse the table and answers the following questions:

(A) Which Heater has higher resistance?
(B) If 1KWh is priced at 30 paise, which heater wilt be costlier if they run for 1 hours each?

Question 4.
Prateek bought a new battery for his Laptopas the earlier battery would not stay charged for more than 5 minutes. He Learnt that a battery consisted of celLs combined together in a particular manner.

The proper representation of series combination of cells obtaining maximum potential is:

(a) (I)
(b) (II)
(c) (III)
(d) (IV)

Question 5.
Take a nichrome wire, a torch bulb, a 10 W bulb and an ammeter (0 – 5 A range), a plug key and some connecting wires. Set up the circuit by connecting four dry cells of 1.5 V each in series with the ammeter leaving a gap XV in the circuit, as shown in Fig. below.

Complete the circuit by connecting the nichrome wire in the gap XY Plug the key. Note down the ammeter reading. Take out the key from the plug. Replace the nichrome wire with the torch bulb in the circuit and find the current through it by measuring the reading of the ammeter. Now repeat the above step with the 10 Wbu(bin the gap XY

Next, complete an electric circuit consisting of a cell and ammeter, a nichrome wire of Length l [say, marked (1)] and a plug key, as shown in Fig. below.

Now, plug the key. Note the current in the ammeter. Replace the nichrome wire by another riichrome wire of same thickness but twice the length, that is 21 [marked (2) in the Fig. Note the ammeter reading. Now replace the wire by a thicker nichrome wire, of the same length l [marked (3)]. A thicker wire has a larger cross-sectional area. Again note down the current through the circuit Instead of raking a nichrome wire, connect a copper wire [marked (4) in Fig.] in the circuit Let the wire be of the same length and same area of cross-section as that of the first nichrome wire [marked (1)].
(A) The observation regarding ammeter readings on connecting the different components nichrome wire, torch bulb and a 10 w bulb in the gap XY is tabulated below.
Select the row containing the correct observation and its explanation.

 Observation Explanation (a) Reading of ammeter will be same in all cases Current flowing in a circuit depends only on the potential difference (b) Reading of ammeter will be same in all cases All the components used are good conductors of electric current. (c) Reading of ammeter will be different for different All components resist the flow of electric current by different amounts components (d) Reading of ammeter will be different for different components All components offer equal resistance to the flow of electric current.

(c) Observation: Reading of ammeter will be different for different components: Explanation: All components resist the flow of electric current by different amounts

Explanation: The current is different for different components as certain components offer an easy path for the flow of electric current while the others resist the flow. The motion of electrons through a conductor isretarded by its resistance.

(B) Refer to the second activity and select the incorrect observations:
(I) The ammeter reading will be same in both cases when nichrome wire, marked (1), and copper wire, marked (4), both of length l and area of cross-section A are connected one by one in the circuit.
(II) The ammeter reading will be different in both cases when nichrome wire, marked (1), and copper wire, marked (4), both of same length and cross-section are connected one by one in the circuit.
(III) The current will be double when nichrome wire, marked (2), of length 21 and area of cross-section A is connected as compared to nichrome wire, marked (1) of length l and area of cross-section A.
(IV) The current will be double when nichrome wire, marked (3), of length l and area of cross-section 2A is connected as compared to nichrome wire, marked (1) of length l and area of cross-section A.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) (I), (III) and (IV)
(a) Both (I) and (II)

Explanation: The ammeter reading will be different in both cases when nichrome wire, marked (1), and copper wire, marked (4), both of same length and cross section are connected one by one in the circuit. This is because copper and nichrome are made up of different materials and resistance of a wire depends on the nature of the material.

The current will be double when nichrome wire, marked (3), of length l and area of cross section 2A is connected as compared to nichrome wire, marked (1) of length l and area of cross section A. This is because a thicker wire offers lesser resistance and hence current flowing will be more through a thicker wire as compared to a thinner wire. However, on increasing the length of a conductor to 21. the resistance also becomes double and therefore current decreases to half of its value.

(C) Select the incorrect statement:
(a) The flow of electrons within a conductor is restrained by the attraction of the atoms among which they move.
(b) The electrons are completely free to move within a conductor.
(c) The motion of electrons through a conductor is retarded by its resistance.
(d) A component of a given size that offers a low resistance is a good conductor.

(D) What will be the effect on current flowing in the circuit when length is made double?
(a) Current will remain same
(b) Current will become double
(c) Current will become half
(d) Current will become four times

(E) What will be the least count of an ammeter of range 0 – 1.5 A shown below:

(a) 0.1 A
(b) 0.2 A
(c) 0.02 A
(d) 0.05 A

Question 6.
Wires used for electrical connections have different properties and hence different ratings. So, one must select wires of proper rating to be used for different appliances as different appliances have different requirements.

Electrical resistivity of a given metallic wire-depends upon:
(a) Its Length
(b) Its thickness
(c) Its shape
(d) Nature of the material

Question 7.
Join three resistors of different values, say, 1 Ω, 2Ω and 3 Ω etc.. and a battery of 6 Vin series. Connect them with a battery, an ammeter and a plug key, as shown in Fig. below.

Plug the key. Note the ammeter reading. Change the position of ammeter to anywhere in between the resistors. Note the ammeter reading each time.

In the next activity. insert a voltmeter across the ends X and Y of the series combination of three resistors as shown in Fig. below. Plug the key in the circuit and note the voltmeter reading. It gives the potential difference across the series combination of resistors. Let it be V. Now measure the potential difference across the two terminals of the battery. Compare the two values. Take out the plug key and disconnect the voltmeter. Now insert the voltmeter across the ends X and P of the first resistor, as shown in

Plug the key and measure the potential difference across the first resistor. Let it be V1. Similarly, measure the potential difference across the other two resistors, separately. Let these values be V2 and V3, respectively.

(A) Refer to the first activity and circuit diagram at fig. 1. A student recorded his observations in a tabuLar form as shown below. SeLect the row containing correct observations/readings.

(a) Position of Ammeter: Between battery and 1 O resistor as shown in figure; Ammeter Beading: 1A; Voltmeter Reading: 6 V.

Explanation: The value of the current in the ammeter is the same and does not depend on its position in the electric circuit.
The total resistance resistance = R1 + R2 + R3 = 6 D.
Therefore, reading of ammeter = I = V / R = 6/6 A = 1 A

(B) Select the correct concLusion based the observations recorded in activity 1 above:
(I) The resistances R1, R2 and R3 are connected in series in the activity.
(II) In a series combination of resistors the current is different in different parts of the circuit.
(III) In a series combination of resistors the current is the same through each resistor.
(IV) In a series combination of resistors the potential difference is the same across each resistor.
(a) Both (I) and (II)
(b) Both (II) and (III)
(C) Both (I) and (III)
(d) Both (II) and (IV)

(C) In the second activity (refer fig. 2), the values of potential difference V, V1, V2 and V3 are:
(a) V = 6 V, V1 = 1 V, V2 = 2 V, V3 = 3 V
(b) V = 6 V, V1 = 1V, V2 = 2 V, V3 = 3 V
(c) V = 6 V, V1 = 1 V, V2 = 2 V, V3 = 3 V
(d) V = 6 V, V1 = 1 V, V2 = 2 V, V3 = 3 V
(d) V = 6 K V1 = 1 V, V2 = 2 K V3 = 3 V

Explanation: The potential difference across the resistors R1, R2 and R3 can be calculated by applying Ohm’s law.
As current I = 1 A, V1 = IR1 = 1 V. Similarly, V2 = 2 V and V3 = 3V.
The potential difference V is equal to the sum of potential differences V1, V2, and V3.

(D) Which of the following relations for V and I is correct for a series combination of three resistors as shown above?
(a) I = I1 + I2 + I3
(b) V = V1 + V2 + V3
(c) $$\frac{1}{V}=\frac{1}{V_{1}}+\frac{1}{V_{2}}+\frac{1}{V_{3}}$$
(d) $$\frac{1}{I}=\frac{1}{I_{1}}+\frac{1}{I_{2}}+\frac{1}{I_{3}}$$

(E) Suppose in the above activity, each resistance is doubled. Select the correct observation:
(a) The total current is doubled
(b) The potential difference is doubled
(c) The total current is halved
(d) The potential difference is halved.

Question 8.
Rahman wanted to change the electric bulb in his study room as he felt that the present bulb was not bright enough for him to study properly. So, he called the electrician. The electrician came and changed the bulb by holding the illuminated bulb with a piece of cloth as the bulb was very hot.

The temperature of the filament of bulb is 2700°C when it glows. Why does it not getburnt up at such high temperature?

Question 9.
Electric force is the force that pushes apart two like charges, or that pulls together two unlike charges. The electric potential (also called the electric field potential, potential drop, the electrostatic potential) is the amount of work energy needed to move a unit of electric charge (a Coulomb) from a reference point to the specific point in an electric field. The graph of variation of electric potential arising from a point charge Q with distance r from the charge q is shown below:

Note: Both the charges Q and q are positive charges.
(A) The conclusion that can be made from the above graph between electric potential (V) and distance (r) from the given charge is:
(I) The electric potential decreases as the point charge Q is brought near the given charge q.
(II) The electric potential of a given charge q is inversely proportional to the distance of the point charge from the given charge.
(III) Work is done on a charge to move it closer to another charge of the same sign.
(IV) Less energy is required to bring the point charge Q closer to the given charge q.
Which of the above conclusions are correct?
(a) Both (I) and (II)
(b) Both (II) and (IV)
(c) Both (I) and (III)
(d) Both (II) and (III)

(B) The unit of electric potential is:
(a) J/C
(b) JC
(c) J/s
(d) J/A

(C) The work done in moving a charge of 5 C across two points having a potential difference 12 V is:
(a) 2.4 J
(b) 60 J
(c) 0.42 J
(d) 120 J

(D) The instrument which is used to measure potential difference between two points and type of connection is given below. Select the row containing the correct information.

 Name of instrument Type of connection (a) Ammeter Series (b) Voltmeter Parallel (c) Voltmeter Parallel (d) Voltmeter Series

(E) When 120 J work is done to move 8 C charge from one point to another in an electric field, the potential difference developed between the two points is:
(a) 15 V
(b) 960 J
(c) 960 V
(d) 7.5 V
(D) (c) Name of instrument: Voltmeter; Type of connection: Parallel
Explanation: The instrument used to measure the potential difference between two points is voltmeter and is always connected in parallel across thepoints between which the potential difference is to be measured.

Question 10.
Potentiometers, or spots” for short, are used for volume and tone control in electric guitars. They allow us to alter the electrical resistance in a circuit at the turn of a knob. The guitar pickups provide the voltage and current source, while the potentiometers provide the resistance. From Ohm’s Law, we can see how increasing resistance decreases the flow of current through a circuit while decreasing the resistance increases the current flow. If two circuit paths are provided from a common voltage source, more current will flow through the path of least resistance.

We can visualize the operation of a potentiometer from the drawing below.

Imagine a resistive track connected from terminal 1 to 3 of the pot. Terminal 2 is connected to a wiper that sweeps along the resistive track when the potentiometer shaft is rotated from 0° to 300°. This changes the resistance from terminals 1 to 2 and 2 to 3 simultaneously, while the resistance from terminals 1 to 3 remains the same. As the resistance from terminal 1 to 2 increases, the resistance from terminal 2 to 3 decreases, and vice-versa.

(A) When we turn the knob in the potentiometer or pots used in electric guitars, it alters the:
(a) Resistivity of the circuit
(b) Resistance in the circuit
(c) Voltage in the circuit
(d) Effective resistance of the circuit.

(B) Four statements are given below regarding the “cold” and “hot” terminals in the diagram of potentiometer.
Select the correct statements:
(I) The “cold” terminal refers to 0° rotation of the potentiometer shaft and the “hot” terminal refers to 300° rotation of potentiometer shaft.
(II) The “cold” terminal refers to 300° rotation of the potentiometer shaft and the “hot” terminal refers to 150° rotation of potentiometer shaft.
(III) When shaft is at “cold” terminal, resistance in the circuit is maximum, whereas it is minimum when shaft is at “hot” terminal.
(IV) When shaft is at “cold” terminal, resistance in the circuit is minimum, whereas it is maximum when shaft is at “hot” terminal.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
(c) Both (I) and (IV)

Explanation: When the potentiometer shaft is turned at 0°, it refers to the “cold” terminal and at this position the resistance is minimum. When the potentiometer shaft is turned at 300°, it refers to the “hot’’ terminal and at this position the resistance is maximum.

(C) When the shaft undergoes 50% rotation, the effective resistance between its terminals is:
(a) R
(b) R/3
(c) 2R
(d) R/2

(D) The device that is used to change resistance in a circuit is:
(a) Rheostat
(b) Fuse
(c) Transformer
(d) Circuit breakers
(a) Rheostat

Explanation: in many cases it may be necessary to increaseor decrease the current in an electric circuit. A component used toregulate current without changing the voltage source is called variabLeresistance. In an electric circuit, a device called rheostat is used tochange the resistance in the circuit.

(E) The table below lists the change in resistance of a wire on changing the physical parameter such as length (l) and area of cross section (A) of the wire. Select the row containing the income Answer:

 Change in Parameter Change in Value of Resistance (a) Length is tripled Resistance becomes three times (b) Area is halved Resistance becomes double (c) Wire is pulled to double its Length Resistance becomes double (d) Diameter is doubted Resistance becomes one fourth

Question 11.
Ohm law’s application ranges from household appliances like heaters to the high tension wires and massive projects like rockets and spaceships. Ohm’s law is used to maintain the desired voltage drop across the electronic components. Ohm’s law is also used in dc ammeter and other dc shunts to divert the current. We can control the speed of the fans at our homes by moving the regulator to and fro. Here the current flowing through the fan is controlled by regulating the resistance through the regulator. A circular knob on the component can be rotated to achieve a variable resistance on the output terminals. For any specific value of the input, we can calculate the resistance, current and thus power flowing through Ohm’s Law.

(A) Refer to the figure-2 above. Select the row containing the correct information:

(B) The current flowing through a fan is controlled by:
(a) Regulating the voltage through the regulator
(b) Regulating the speed through the regulator
(c) Regulating the resistance through the regulator
(d) Regulating the resistivity through the regulator

(C) A resistance of 5 ohms is further drawn so that its length becomes double. Its resistance will now be:
(a) 20 ohms
(b) 10 ohms
(c) 7.5 ohms
(d) 5 ohms

(D) For a fixed supply voltage the current flowing through a conductor will decrease when
(a) The cross-sectional area of the conductor is increased
(b) The length of the conductor is increased
(c) The length of the conductor is decreased
(d) The cross-sectional area is increased and length is decreased

(E) Observe the V-l graph plotted below and select the incorrect observations:

(I) The graph between current (I) and potential difference (V) is a straight line not passing through the origin.
(II) With increase in potential difference, current flowing through the conductor increases.
(III) The slope of the above graph gives the resistivity of the conductor.
(IV) The resistance of the given conductor is 25 Ohm.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) Both (111) and (IV)

(C) (a) 20 ohms
Explanation: When a 5 ohm resistance is drawn so that its length becomes double, the area of cross section becomes half. As
R = ρ$$\frac{l}{A}$$ = 5 Ohm, the new resistance will be A
R’ = ρ$$\frac{2l}{A/2}$$ = 4 × ρ$$\frac{l}{A}$$ = 4 × 5 = 20 Ohm.

Question 12.
Electric heaters, toasters, geysers, iron and kettles are common appliances used throughout the world. The heaters have a metal coil that has high resistance that permits a certain amount of current to flow through them to provide the required heat as per the Joule’s law of heating. The electric kettle and irons have a lot of resistors in them. The resistors limit the amount of current to flow through them to provide the required amount of heat. The size of resistors used in them is determined by using Ohm’s Law.

(A) According to Joule’s law of heating, the heat produced in a resistor in time t is:
(I) Directly proportional to the square of current for a given resistance
(II) Inversely proportional to the potential difference across the resistance
(III) Directly proportional to resistance for a given current
(IV) Inversely proportional to the time for which the current flows through the resistor.
Select the correct statements.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (I) and (III)
(d) Both (I) and (III)

Explanation: According to Joule’s law of heating, the heat produced in a resistor in time t is given by H = Pt = Vlt = l2Rt ⇒H ∝ l2, H ∝ R, H ∝ t

(B) If the resistance of a resistor is reduced to half of its initial value, potential difference remaining unchanged, the heating effects in the resistor will become:
(a) Half
(b) One fourth
(c) Two times
(d) Four times

(C) Another common application of Joule’s heating is the fuse used in electric circuits. Select the incorrect statement regarding fuse:
(a) It protects circuits and appliances by stopping the flow of any unduly high electric current.
(b) The fuse is placed in parallel with the device.
(c) It consists of a piece of wire made of a metal or an alloy of appropriate melting point.
(d) If a current larger than the specified value flows through the circuit, the fuse wire melts and breaks the circuit.

(D) Consider an electric iron which consumes 1 kW electric power when operated at 220 V. The table below gives the rating of ideal fuse that should be used in this case and the heat generated in the electric iron in 30 seconds.

 Ideal Rating of Fuse (A) Heat Generated in 30 s (J) (a) 4A 3.0 × 104 (b) 10A 1.0 × 104 (c) 5A 3.0 × 104 (d) 5A 3.6 × 106

(E) A resistance of 30 ohm is connected to a 6 V battery. The heat energy in joules generated per minute will be:
(a) 72 J
(b) 144 J
(c) 288 J
(d) 36 J
(A)
(E) (a)72J
Explanation: The heat generated in a resistor is given by Joule’s law of heating,
H = I2Rt.
Here, I = $$\frac{V}{R}=\frac{6}{30}$$ = 0.2A , R = 30 Ohm and t = 60 s.
Therefore, H = (0.2)2 × 30 × 60 = 72 J

Question 13.
Electrical energy is the energy derived from electric potential energy or kinetic energy of the charged particles. In general, it is referred to as the energy that has been converted from electric potential energy. In many cases it is necessary to calculate the energy usage by an electric device or a collection of devices, such as in a home. The electrical energy (E) used can be reduced either by reducing the time of use or by reducing the power consumption of that appliance or fixture. This will not only reduce the cost, but it will also result in a reduced impact on the environment. Improvements to lighting are some of the fastest ways to reduce the electrical energy used in a home or business. About 20% of a home’s use of energy goes to lighting, while the number for commercial establishments is closer to 40%. A few common electrical appliances and their power ratings are given below:

 Load Types Power Ratings (1) Light bulbs (incandescent) 60W, 80W, 100W (2) Electric (steam) iron 2400W (3) Standing fan 70W (4) Water heater/Kettle 2000W (5) Electric blender 350W (6) Refrigerator 200W (7) Microwave oven 1200W (8) Hand dryer 1800W

(A) Which of the following can be concluded from the table shown above?
(I) The energy consumption of an electrical appliance depends on the power rating and the usage time.
(II) The larger the power rating in the electrical appliance, the lesser is the energy used every second.
(III) The Longer the usage time, the more electrical energy is consumed.
(IV) Appliances that have a heating effect usually have a high power rating and consume more electricity.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (II) and (IV)
(d) (I), (III) and (IV)

(B) An electrical water heater/kettle which is marked 2000 W, 220 V means that:
(a) The electric kettle will consume 2000 J of electrical energy every 1 second if it is connected to a 220 V supply.
(b) The electric kettle will consume 7.2 X 106 J of electrical energy every 1 second if it is connected to a 220 V supply.
(c) The electric kettle will consume 440 J of electrical energy every 1 second if it is connected to a 220 V supply.
(d) The electric kettle will consume 3.6 X 106 J of electrical energy every 1 second if it is connected to a 220 V supply.

(C) Students calculated the number of electrical units consumed daily by operating a hand dryer (Power rating 1800 W) for 2 h daily on a supply of 220 V, the total electrical energy consumed in the month of June (in Joule) and the cost of electricity for the month of June if one unit costs Rs. 5.50 and assuming that no other appliance is used.
Select the row containing the correct entries.

(D) The resistance of the refrigerator (Power rating 200 W, 220 V) is:
(a) 44 kilo Ohm
(b) 44 Ohm
(c) 242 Ohm
(d) 484 Ohm

(E) If the microwave oven and the electric blender of power ratings 1200 W and 350 W respectively are both used for 5 hours daily, the electrical energy consumed in a day is:
(a) 6.0 units
(b) 7.75 units
(c) 15.5 units
(d) 232.5 units
(E) (b) 7.75 units
Explanation: The electrical energy consumed in a day is given by E = Pt = 1200 × 5 + 350 × 5 Wh = 7750 Wh = 7.75 kWh or 7.75 units

Question 1.
Define resistance. Give its S.i. unit.

Question 2.
Define the term electrical resistivity of a material.
Electrical resistivity is defined as the electrical resistance of a conductor having cross¬sectional area 1 m2 and a length 1 m.

Related Theory

• SI unit of electrical resistivity is ohm m (Wm)
• It is a characteristic property of the material and varies with temperature.
• Metals and alloys have very low resistivity but insulators have very high resistivity.

Question 3.
How will the heat produced in a resistor R change if its resistance is reduced to half of its initial value, other parameters of the circuit remain unchanged?

Question 4.
The temperature of the filament of bulb is 2700°C when it glows. Why does it not get burnt up at such high temperature?
Filament of bulb is made using strong metals having high melting points such as Tungsten which has melting point of 3380 °C, which is higher than the temperature at which it glows

Question 5.
Should the resistance of an ammeter below or high? Give reason.

Question 6.
Two unequal resistances are connected in parallel. If you are not provided with any other parameters (eg. Numerical value of I and R). What can be said about the voltage drop across the tow resistors?

1. Voltage-drop is same across both the resistors. Explanation: In parallel connection, all the elements are connected between same two points hence the voltage drop across any number of resistors or other elements
2. Connected in parallel is same. Thus the voltage drop across the two resistors is same

Question 7.
Some work is done to move a charge Q from infinity to a point A in space. The potential of the point? A is given as V. What is the work done to move this charge from infinity in terms of Q and V?

## MCQ Questions for Class 10 Science Chapter 10 Light Reflection and Refraction with Answers

Students can also read Online Education MCQ Questions for Class 10 Science Chapter 10 Light Reflection and Refraction Questions with Answers hope will definitely help for your board exams. https://ncertmcq.com/mcq-questions-for-class-10-science-with-answers/

## Online Education Light Reflection and Refraction Class 10 MCQs Questions with Answers

Light Reflection And Refraction Class 10 MCQ Question 1.
Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively, as shown in the figure. Which of the following could be inside the box?

(a) A rectangular glass slab
(b) A convex lens
(c) A concave less
(d) A prism

Light Class 10 MCQ Question 2.
A beam of light is incident through the holes on side A and emerges out of the holes on the other face of the box as shown in the figure. Which of the following could be inside the box?

(a) Concave lens
(b) Rectangular, glass slab
(c) Prism
(d) Convex lens
(d) Convex lens

Explanation: In the given diagram, parallel rays converge at a point and emerge from face B. So, there will be a convex lens inside the box.

Class 10 Light MCQ Question 3.
When an object is kept within the focus of a concave mirror, an enlarged image is formed behind the mirror. This image is:
(a) real
(b) inverted
(c) virtual and inverted
(d) virtual and erect

MCQ Of Light Class 10 Question 4.
A full length image of a distant tall building can definitely be seen by using:
(a) a concave mirror
(b) a convex mirror
(c) a plane mirror
(d) both concave as well as plane mirror

Class 10 Light Reflection And Refraction MCQ Question 5.
Your school laboratory has one large window. To find the focal length of a concave mirror using one of the walls as screen, the experiment may be performed:
(a) on the same wall as the window.
(b) on the wall adjacent to the window.
(c) on the wall opposite to the window.
(d) only on the table as per laboratory arrangement.
(d) only on the table as per laboratory arrangement.

Class 10 Science Chapter 10 MCQ Question 6.
The path of a ray of light coming from air passing through a rectangular glass slab is traced by four students shown as A, B, C and D in the figure. Which one of them is correct?

MCQ On Light Class 10 Question 7.
In order to determine the focal length of a concave mirror by obtaining the Image of a distant object on screen, the position of the screen should be:
(a) parallel to the pLane of concave mirror
(b) perpendicular to the plane of concave mirror
(c) IncLined at an angle 600 to the plane of mirror
(d) in any direction with respect to the plane of concave mirror [Dikshaj
(a) parallel to the plane of concave mirror

Explanation: AD the refLected light rays converge and pass through the focus (F) of a concave mirror. Since the focus of a concave mirror is in front of the mirror, the screen has to be placed parallel in front of the mirror.

Light Reflection And Refraction MCQ Question 8.
A student carries out the experiment of tracing the path of a ray of Light through a rectangular glass slab for two different values of angLe of incidence ∠i = 300 and ∠i = 45° In the two coses the student is likely to observe the set of vaLues of angle of refraction and angLe of emergence as
(a) ∠r =30, ∠e = 20° and ∠r = 45’, ∠e = 28°
(b) ∠r =30°. ∠e = 30° and ∠r=45°, ∠e= 450
(c) ∠r =200, ∠e = 30° and ∠r = 28°, ∠e=45°
(d) ∠r =20°, ∠e = 20° and ∠r = 28°, ∠e = 28°
(c) ∠r=20° ∠e=30° and ∠r= 28 ∠e=45°

Related Theory:
The angle of refraction must be less than the angle of incidence. White angle of emergence is equal to angle of incidence.
for ∠i = 300. ∠r = 20° and ∠e = 30
for ∠i = 450e ∠r = 28° and ∠e = 45°

Reflection Of Light Class 10 MCQ Question 9.
If you focus a distant object of the shape using a concave mirror, the Image obtained must be of the shape

Light Chapter Class 10 MCQ Question 10.
In which of the following diagrams has the protractor (D) been correctly placed to measure the angle of incidence and the angle of emergence?

a) I, III
(b) I, IV
(c) II, III
(d) II, IV
(a) I, III

Explanation: The angle of incidence is the angle between the incident ray and the normal at the point of incidence. The angle of emergence is the angLe between the emergent ray and the normal at the point of emergence.

Moreover, the protractor should always be placed in such a way that its base is always along the normal of the incident ray or the emergent ray.

Ch 10 Science Class 10 MCQ Question 11.
An optical device has been given to a student and he determines its focal Length by focusing the image of the sun on a screen placed 24 cm from the device on the same side as the sun. Select the correct statement about the device.
(a) Convex mirror of Focal Length 12 cm
(b) Convex Lens of focal Length 24 cm
(c) Concave mirror of focal length 24 cm
(d) Convex tens of Focal Length 12 cm

MCQ Of Light Reflection And Refraction Class 10 Question 12.
A student is performing the experiment of determining the Focal Length of a given concave mirror by focussing a distant tree on a screen. Which one of the following kinds of images he is likely to obtain on the screen?

(a) (I)
(c) (III)
(b) (II)
(d) (IV)

Explanation: A concave mirror forms a real and inverted image of a distant object, such as tree, at its focus.

Class 10 Science Ch 10 MCQ Question 13.
A student has focussed on the screen a distant building using a convex lens. If he has selected a blue coloured building as object, select from the following options the one which gives the correct characteristics of the image formed on the screen.
(a) Virtual, erect, diminished and green shade
(b) Real, inverted, diminished and in violet shade
(c) Real, inverted, diminished and in blue shade
(d) Virtual, inverted, diminished and in blue shade
(c) Real, inverted, diminished and in blue shade

Explanation: As the student has focussed a distant blue coloured building on the screen using a convex lens, a real inverted and diminished image is formed at the principal focus of the convex lens.

As object is quite far, a diminished image will be formed at the principal focus.

The colour of image will be same as colour of the object because no change in colour takes place during refraction.

MCQ Questions On Light Class 10 Question 14.
Study the following four experimental setups by four students A, B, C and D showing the incident ray to trace the path of a ray of light through a glass slab. Which of these will get the best result?

(a) (I)
(b) (II)
(c) (III)
(d) (IV)

Light And Reflection Class 10 MCQ Question 15.
The focal length of the concave mirror in the following experimental set-up is:

(d) 6.6 cm

Explanation: The least count of optical bench $$\frac{1}{5}$$cm = 0.2 cm
Position of the concave mirror = 12.8 cm
Position of the screen = 6.2 cm
Focal length of the concave mirror = distance of the screen from the pole of the concave mirror = 12.8 – 6.2 cm = 6.6 cm

Light Class 10 MCQ With Answers Question 16.
Three students A, B and C focussed a distant building on a screen with the help of a concave mirror. To determine focal length of the concave mirror they measured the distances as given below:
Student A: From mirror to the screen
Student B: From building to the screen
Student C: From building to the mirror
Who measured the focal length correctly:
(a) Only A
(b) Only B
(c) A and B
(d) B and C
(a) Only A

Explanation: A concave mirror forms a distinct image of a distant object at its focus. As student ‘A’ measures the distance between mirror to the screen to find the focal length, he measured the focal length correctly.

MCQ Questions For Class 10 Science Chapter 10 Question 17.
A student has traced the path of a ray of light through a glass slab as follows. If you are asked to label 1, 2, 3 and 4, the correct sequencing of labelling Zi, Ze, Zr and lateral displacement respectively is

(a) 2,1, 3, 4
(b) 1, 2, 3, 4
(c) 1, 3, 2, 4
(d) 1, 3, 4, 2
(c) 1, 3, 2, 4

Related Theory
Angle of emergence (e): The angle of the light coming out of a medium.
Lateral displacement: The perpendicular distance between the incident ray and the emergent ray.

Light Reflection And Refraction Class 10 MCQ With Answers Question 18.
A student determines the focal length of a device X by focusing the image of a distant object on a screen placed 20 cm from the device on the same side as the object.
The device X is
(a) Concave lens of focal length 10 cm
(b) Convex lens of focal length 20 cm
(c) Concave mirror of focal length 10 cm
(d) Concave mirror of focal length 20 cm

Chapter 10 Science Class 10 MCQ Question 19.
A student obtained a sharp image of a candle flame placed at the distant end of the laboratory table on a screen using a concave mirror to determine its focal length. The teacher suggested him to focus a distant building about 1 km far from the laboratory, for getting more correct value of the focal length. In order to focus the distant building on the same screen the student should slightly move the:
(a) mirror away from the screen
(b) screen away from the mirror
(c) screen towards the mirror
(d) screen towards the building
(c) screen towards the mirror

Question 20.
A student obtains a sharp image of the distant window (W) of the school laboratory on the screen (S) using the given concave mirror (M) to determine its focal length. Which of the following distances should he measure to get the focal length of the mirror?

(a) MW
(b) MS
(c) SW
(d) MW – MS

Question 21.
The image formed by a plane mirror is:
(a) virtual, behind the mirror and enlarged
(b) virtual, behind the mirror and of the same size as the object
(c) real, at the surface of the mirror and enlarged
(d) real, behind the mirror and of the same size as the object
(b) Virtual, behind the mirror and of the same size as the object

Question 22.
When object moves closer to convex lens, the image formed will be
(a) away from the lens on the other side of lens.
(b) towards the lens.
(c) away from the lens on the same side of an object.
(d) first towards and then away from the lens.

Question 23.
Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in figure?

Explanation: Ray of light parallel to the principal axis towards the mirror after reflection from the mirror will pass through the focus.

Question 24.
The refractive index of four substances P, Q, R and S are 1.50, 1.36, 1.77 and 1.31 respectively. The speed of light is the maximum in the substance:
(a) P
(b) Q
(c) R
(d) S

Question 25.
Which one of the following materials cannot be used to make a lens?
(a) Water
(b) Glass
(c) Plastic
(d) Clay
(d) Clay

Explanation: Clay is opaque and does not let light to pass through it.

Question 26.
A small bulb is placed at the focal point of a converging lens. When the bulb is switched on, the lens produces:
(a) a convergent beam of light
(b) a divergent beam of light
(c) a parallel beam of light
(d) a patch of coloured light
(c) A parallel beam of light

Explanation: When an object is placed at the focus of a convex lens, the convex lens convert the diverging rays of light coming from the object into a parallel beam of light rays which form an image at infinity.

Question 27.
In torches, search lights and headlights of vehicles, the bulb is placed:
(a) between the pole and the focus of the reflector
(b) very near to the focus of the reflector
(c) between the focus and centre of curvature of the reflector
(d) at the centre of curvature of the reflector

Question 28.
You are given water, mustard oil, glycerine and kerosene. In which of these media, a ray of light incident obliquely at some angle would bend the most? (Refractive index of water = 1.33, Mustard oil = 1.46, Glycerine = 1.473, Kerosene = 1.44)
(a) Kerosene
(b) Water
(c) Mustard oil
(d) Glycerine
(d) Glycerine

Explanation: Out of the given four materials, the refractive index of glycerine is highest. So, greatest deviation of incident light ray is observed in case of glycerine.

Related Theory
A substance having higher refractive index is optically denser than another substance having lower refractive index. We can conclude, the higher the refractive index of a substance, more it will change the direction of a beam of light passing through it.

Question 29.
A student obtained a sharp inverted image of a distant tree on the screen placed behind a convex lens. He then removed the screen and tried to look through the lens in the direction of the object. He would now observe:
(a) a blurred image on the wall of the laboratory
(b) an erect image of the tree on the lens
(c) no image as the screen has been removed
(d) an inverted image of the tree at the focus of the lens

Question 30.
Magnification produced by a rear view mirror fitted in vehicles:
(a) is less than one
(b) is more than one
(c) is equal to one
(d) can be more than or less than one depending upon the position of the object in front of it.
(a) is less than one

Explanation: Convex mirror is used as a rear view mirror in vehicles. It forms virtual, erect and diminished images of the objects.

As magnification is defined as the ratio of the height of the image to the height of the object, hence, magnification produced by a rearview

Question 31.
You are provided four convex lenses of focal length 10 cm, 20 cm, 30 cm and 40 cm. Which out of the four lenses will converge light the most and the least?
Select the row containing the correct answer and reason:

Question 32.
A student-focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as under
Position of candle = 26.0 cm
Position of convex lens = 50.0 cm
Position of the screen = 90.0 cm
Students noted down the values of object distance (u), image distance (v) and also calculated the focal length (f) of the convex lens used.

Select the row containing the correct values as per the sign convention:

Question 33.
Select the correct statements from the statements given below regarding refraction of light when light is incident from a medium A having refractive index 1.85 on a glass slab having refractive index 1.50.
(I) Light will bend towards the normal in the glass slab.
(II) Emergent ray will be parallel to the refracted ray.
(III) Speed of light will be more in glass slab as compared to medium A.
(IV) Angle of refraction will be more than angle of incidence.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (II) and (IV)
(d) Both (III) and (IV)
(d) Both (III) and (IV)

Explanation: As light is incident from the medium A having higher refractive index than glass, speed of light will be less in medium A as compared to glass. When light traveLs from a denser to a rarer medium, it bends away from the normal. Therefore, angle of refraction will be greater than the angle of incidence.

Question 34.
Four statements are written below which are the general rules for drawing ray diagrams in case of lenses. Select the incorrect statements:
(I) A ray of light from the object, parallel to the principal axis, after refraction from a concave lens, passes through the principal focus on the other side of the lens.
(II) A ray of light appearing to meet at the principal focus of a convex lens, after refraction, will emerge parallel to the principal axis.
(III) A ray of light passing through a principal focus, after refraction from a convex lens, will emerge parallel to the principal axis.
(IV) A ray of light passing through the optical centre of a lens will emerge without any deviation.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (III) and (IV)

Question 35.
Given below are statements regarding sign conventions for reflection by spherical mirrors. Select the correct statements.
(I) All distances parallel to the principal axis are measured from the pole of the mirror.
(II) All the distances measured to the left of the origin (along – x-axis) are taken as positive while those measured to the right of the origin (along + x-axis) are taken as negative.
(III) Distances measured perpendicular to and above the principal axis (along + y-axis) are taken as positive.
(IV) Distances measured perpendicular to and above the principal axis (along +y-axis) are taken as negative.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (III)
(d) Both (III) and (IV)

Question 36.
Refractive indices of turpentine oil, sapphire, water and crown glass are 1.47, 1.77, 1.33 and 1.52 respectively. In which of these media will a ray of light incident obliquely at the same angle from air would bend the least?
(a) Turpentine oil
(b) Sapphire
(c) Water
(d) Crown glass
(c) Water

Explanation: The speed of light in a medium is inversely proportional to the refractive index of the medium. And the amount of bending is also inversely proportional to the refractive index of the medium. As the refractive index of water is the least out of the given media, it is optically rarer as compared to the other media. So, light will bend the least in water.

Question 37.
Kaashvi performed an activity using a concave mirror of focal length 20 cm. She placed the object 30 cm in front of the mirror. Where is the image likely to be formed?
(a) At 10 cm behind the mirror
(b) At 10 cm in front of the mirror
(c) At 60 cm in front of the mirror
(d) At 60 cm behind the mirror

Question 38.
The angle between the incident and reflected rays is 90° as shown below:

If the plane mirror is rotated by 10° about O in the anti-clockwise direction, then the angle between the incident and reflected rays will be:
(a) 55°
(b) 90°
(c) 100°
(d) 110°

Question 39.
Two lenses, a convex lens of focal length 20 cm and a concave lens of focal length 25 cm, are held close to each other. The focal length of the combination of the lenses is:
(a) + 45 cm
(b) – 5 cm
(c) – 45 cm
(d) + 100 cm
(d) + 100 cm

Explanation: The power of combination of two lenses is P = P1 + P2, where P1 is the power of the convex lens of focal length 20 cm and P2 is power of the concave lens of focal length 25 cm.

As Power (in Dioptre) = P = $$\frac{1}{f(\text { inm })}$$
Therefore, $$\frac{1}{f_{1}}+\frac{1}{f_{2}}=+\frac{100}{20}-\frac{100}{25}$$ = +1
Thus, focal length of combination = +100 cm

Question 40.
Magnification produced by a rear view mirror fitted in vehicles:
(a) is less than one
(b) is more than one
(c) is equal to one
(d) can be more than or less than one depending upon the position of the object in front of it.
(a) is Less than one

Explanation: Convex mirror is used as a rear view mirror in vehicles. It forms virtual, erect and diminished images of the objects.

As magnification is defined as the ratio of the height of the image to the height of the object, hence, magnification produced by a rear view mirror, fitted in vehicles is less than one.

### Assertion Reasoning questions Class 10 Science Chapter 10

For the following questions, two statements are given one labelled Assertion (A) and the Other labelled Reason (R). Select the correct answers to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 41.
Assertion (A): A convex mirror is used as a rearview/driver’s mirror.
Reasoning (R): Convex mirrors have a wider field of view as they are curved outwards. They also give an erect, although diminished image. [Diksha]
(b) Both (A) and (R) are true but (R) is not correct explanation of the assertion. Explanation: Since the image formed is highly diminished in convex mirror, we can see the full image of far away objects, which is otherwise not possible in concave and plane mirrors.

Question 42.
Assertion (A): The word AMBULANCE on the hospital vans is written in the form of its mirror image as AMBULANCE in inverted form.
Reason (R): The image formed in a plane mirror is same size of the object.
(b) Both (A) and (R) are true but (R) is not correct explanation of the assertion.

Explanation: The word AMBULANCE is written backwards (inverted) as when it is seen through a mirror in the vehicles ahead the drivers see it as AMBULANCE without inversion and give way to it on priority.

Question 43.
Assertion (A): Light travels faster in glass than in air.
Reason (R): Glass is denser than air.

Question 44.
Assertion (A): A convex lens has a real focus.
Reason (R): All light rays pass through the focus of a convex lens after refraction.
(c) (A) is true but (R) is false.

Explanation: A convex lens has a real focus as all the light rays parallel to the principal axis actuaLly pass through the focus of the convex lens after refraction. However, rays which are not parallel to the principal axis do not pass through the focus of the convex lens.

Question 45.
Assertion (A): A ray of light passing through the centre of curvature of a concave mirror is reflected back along the same path.
Reason (R): The incident ray, the reflected ray and the normal at the point of incidence lie on the same plane.
(b) Both (A) and (R) are true but (R) is not correct explanation of the assertion. Explanation: A ray of light passing through the centre of curvature of a concave mirror is reflected back along the same path because the rays are incident normally on the mirror. Therefore, angle of incidence = 0° and so, angle of reflection is also 0°. The law of reflection, namely, angle of incidence is equal to the angle of reflection is being followed here.

Question 46.
Assertion (A): The power of a concave lens is negative.
Reason (R): A concave lens has a virtual focus.

(Competency Based Questions (CBQs))

Question 1.
Sushma went with her mother to purchase some gold jewelry for her sister’s marriage. The salesman asked them to check the hallmark and gold purity to ascertain the genuineness of the gold article. As the hallmark was too small to be seen by the naked eye, the salesman gave them a magnifying glass to see the hallmark.

Which type of lens is used as a magnifying glass and why?
A convex lens is used as a magnifying glass as it forms an enlarged or magnified image of an object when it is held close to the object to be seen.

Question 2.
Analyse the following observation table showing variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations:

 S.NO Object-Distance u (cm) Image-Distance v (cm) 1. -60 – +12 2. -30 – +15 3. -20 – +20 4. -15 – +30 5. -12 – +60 6. -9 – +90

(A) What is the focal length of the convex lens? State reason for your answer.
From S.No. 3, we can say that the radius of curvature of the lens is 20 cm because when an object is placed at the centre of the curvature of a convex lens its image is formed on the other side of the lens at the same distance from the lens. And, we also know that focal length is half of the radius of curvature. Thus, focal length of the lens is + 10 cm.

(B) For what object-distance (u) is the corresponding image-distance (v) not correct? How did you arrive at this conclusion?
S.No. 6 is not correct as for this observation the object distance is between focus and pole, and for such cases the image formed is always virtual but in this case, a real image is forming as the image distance is positive.

(C) A concave mirror gives real, inverted and same size image if the object is placed
(a) At focus
(b) At infinity
(c) At C i.e. centre of curvature
(d) Beyond centre of curvature
(c) At C i.e. centre of curvature

(D) Focal length of plane mirror is:
(a) At infinity
(b) Zero
(c) Negative
(d) None of these

Question 3.
While sipping some Lemonade with a straw, Ronit observed that the straw Looked bent when seen from the side. He could guess that it was due to the bending of Light or refraction.

The figure shows a ray of Light as it travels from medium A to medium B. The refractive index of the medium B relative to medium A is

(a) $$\frac{\sqrt{3}}{\sqrt{2}}$$
(b) $$\frac{\sqrt{2}}{\sqrt{3}}$$
(c) $$\frac{1}{\sqrt{2}}$$
(d) $$\sqrt{2}$$
(a) $$\frac{\sqrt{3}}{\sqrt{2}}$$

Explanation: Here, angle of incidence, i = 60° Angle of refraction, r = 45°
The refraction index of the medium B relative to medium A,

Question 4.
Analyze the following table showing refractive indices of four media A, B, C and D and answer the questions that follow:
The refractive indices of four media A, B, C and D are given in the following table:

(A) If light, travels from one medium to another in which case the change in speed will be minimum.
Minimum change is seen as light moves between 1.50 and 1.52, i.e. B and C.

(B) If Light, travels from one medium to another, in which case the change in speed will be maximum.
Maximum change when light moves between 1.33 and 2.40, i.e. A and D.

(C) A Light ray enters from medium A to medium B as shown in the figure. The refractive index of medium B relative to A will be:

(a) Greater than unity
(b) Less than unity
(c) Equal to unity
(d) Zero
(a) Greater than unity

Explanation: Since light rays in medium B goes towards normal. So it has greater refractive index and lesser velocity, of light with respect to medium A. So refractive index of medium B with respect to medium A is greater than unity.

(D) The laws of reflection hold good for
(a) plane mirror only
(b) concave mirror only
(c) convex mirror only
(d) all mirrors irrespective of their shape

Question 5.
Parag along with his friends were experimenting with a concave mirror. They tried to focus the sun’s rays at a piece of paper and observed that the paper started to burn after some time.

Rays from the sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that the size of its image is equal to the size of the object?
(a) 15 cm in front of the mirror.
(b) 30 cm in front of the mirror.
(c) Between 15 cm and 30 cm in front of the mirror.
(d) More than 30 cm in front of the mirror.
(b) 30 cm in front of the mirror.

Explanation: The sun is at an infinite distance from the surface of the Earth. Now, light rays from the sun rays i.e., from infinity, are parallel to the principal axis. After reflection from the concave mirror, the light rays will converge at focus. It is given that the sun rays converge at 15 cm.

So, the focal length of the mirror, f = 15 cm. We know that in case of a concave mirror, the same size, real and inverted image is formed when object is placed at 2F or the centre of curvature.
Hence, in this case, object must be place at 2F i.e., 2 x 15 = 30 cm.

Question 6.
First, hold a convex lens in your hand and direct it towards the Sun. Focus the light from the Sun on a sheet of paper. Obtain a sharp bright image of the Sun. Hold the paper and the lens in the same position for a while. Keep observing the paper. While performing this activity, do not look at the Sun directly or through a lens or otherwise you may damage your eyes if you do so.
Next, take a convex lens. Find its approximate focal length in a way described in Activity above. Draw five parallel straight lines, using chalk, on a long Table such that the distance between the successive lines is equal to the focal length of the lens. Place the lens on a lens stand. Place it on the central line such that the optical centre of the lens lies just over the line. Place a burning candle, far beyond 2F1 – to the left. Obtain a clear sharp image on a screen on the opposite side of the lens. Repeat this Activity by placing object just behind 2F1, between F1 and 2F1, F1 at 1, between F1 and O. Note down and tabulate your observations.
(A) Following observations were recorded by the student after performing the first activity:
(I) A large and bright image of the sun is obtained on a paper when light from sun is focused.
(II) A sharp and bright image of the sun is obtained on a paper when light from sun is focused.
(III) The paper begins to burn immediately when both the paper and lens are held in the same position.
(IV) The paper begins to burn after some time when both the paper and lens are held in the same position.
Select the incorrect observations:
(a) Both (II) and (III)
(b) Both (II) and (IV)
(c) Both (I) and (III)
(d) Both (I) and (IV)
(c) Both (I) and (III)

Explanation: Convex lens is a converging lens. So, it converges the light rays from the sun and a sharp bright image of the sun is obtained on a paper as sun is very very far from us. When the lens and paper are held in the same position for some time, it is observed that the paper begins to burn after some time as all the sun’s rays converge at the bright spot, which is the focus of the lens, causing the paper to burn.

(B) Two students performed the second activity for which as per directions mentioned above.
They drew five lines and marked the line numbers from 1 to 5 above the lines.

The teacher asked the students to keep a record of the lines marked. The students tabulated the record as given below:

 First Student Second Student (a) Line numbers 1 and 2 are 2F1 and F1 respectively Line number 1 and 5 are F1 and 2F1 respectively (b) Line numbers 4 and 5 are F2 and 2F2 respectively Line number 2 and 4 are and F2 respectively (c) The central line (line number 3) contains the focus of the lens The central line (line number 3) contains the optical center (d)Distance between two successive lines is equal to twice the focal length of the lens Distance between two successive lines is equal to the focal length of the lens

Select the row containing the correct information by both the students.
(b) First student: Line numbers 4 and 5 are F2 and 2F2 respectively; Second student: Line number 2 and 4 are F1 and F2 respectively

Explanation: The lens has been placed on the central line which contains the optical centre of the lens. Lines 1 and 2 are 2F1 and F1 respectively and lines 4 and 5 are F2 and 2F2 respectively. Moreover, the distance between successive lines is equal to the focal length of the lens, which is OF1.

(C) Select the incorrect statement. In the first activity:
(a) A real image of the sun is obtained on the paper
(b) A virtual image of the sun is obtained on the paper.
(c) The convex lens converges the sun’s rays at the bright spot.
(d) The approximate focal length of the convex lens is the distance between the lens and the paper.
(b) A virtual image of the sun is obtained on the paper.

Explanation: Convex lens is a converging lens and converges the parallel rays of light coming from the sun at the bright spot formed on the paper. The image formed is therefore real. Further, the distance between the lens and the paper gives the approximate value of the focal length of the lens.

(D) The image of a burning candle placed beyond 2F1 to the left is:
(a) Real, inverted, diminished and formed on a screen placed at the opposite side of the lens.
(b) Real, inverted and enlarged and formed on the same side as the candle.
(c) Virtual, erect, diminished and formed on the same side as the candle.
(d) Real, inverted, enlarged and formed on a screen placed at the opposite side of the lens.

(E) As the candle is brought closer to the focus F-L from the left:
(a) Image becomes smaller in size
(b) Image size first becomes smaller and then enlarges
(c) Image size first becomes larger and then diminishes.
(d) Image becomes Larger in size.

Question 7.
When Aiysha visited her ENT specialist to consult the doctor as she had some problem in her ear, she saw a circular mirror worn by the doctor around the forehead. She wanted to know the purpose served by the mirror. So, she came home and tried to find out the type of mirror and its applications.

Write two different uses of concave mirrors.
Uses of concave mirrors:
(1) It is used in torches, headlights of vehicles and search-lights to get powerful parallel beams of light.
(2) It is used as a shaving mirror to see a larger image of the face when held close to the face.
(3) It is used by dentists and ENT specialists to see larger images of teeth and inner parts of ear and throat.
(4) Large concave mirrors or parabolic mirrors are used in solar furnaces to concentrate sunlight.

Question 8.
There are numerous uses of concave mirrors in daily life. It is used in the aircraft landing to guide the airplane, it is used as a torch to reflect the light rays, it is used during shaving to get an erect and enlarged image of the face, etc.
A student had a concave mirror with him and wanted to know its focal length. So, he performed an activity to find out the focal length of the concave mirror.

(A) The radius of curvature of the concave mirror used by the student in the above activity is:
(a) 60 cm
(b) 40 cm
(c) 30 cm
(d) 10 cm
(a) 60 cm

Explanation: The focal length of the mirror is the distance between the pole of the mirror and the screen where the clear image of the distant object is formed. As the mirror stand is at 10 cm and screen is at 40 cm, therefore, focal length = 40-10 = 30 cm, as the image of a distant object is formed by a concave mirror at its focus. Radius of curvature = 2f = 60 cm.

(B) Select the correct observation :
(I) Image of the distant tree is formed by the concave mirror at its focus.
(II) Image of the distant tree is formed by the concave mirror at its centre of curvature.
(III) Image is virtual and laterally inverted
(IV) Image is real and inverted
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
(c) Both (I) and (IV)

Explanation: A concave mirror forms a real and inverted image of a distant object at its focus as shown in the figure above. Image is real as the rays of light intersect at the focus after reflection from the concave mirror.

(C) It is desired to obtain an erect image of an object, using concave mirror of radius of curvature 40 cm. Two students gave their ideas in a tabular form as given below:

 First Student Second Student (a) Range of object distance should be from 0 cm to less than 20 cm Range of object distance should be from 0 cm to less than 40 cm (b) Image can be obtained at a screen placed at the position of formation of image Image cannot be obtained on a screen placed at the position of formation of image (c) Image will be larger than the object Image will be of same size as the object (d) Image will be formed behind the mirror. Image will be formed behind the mirror.

The row containing the correct information by both the students is:

(D) In the situation mentioned in question (C) above, if the object is kept at 40 cm, the position and nature of image formed will be:
(a) Real, inverted and enlarged image will be formed 40 cm in front of the mirror.
(b) Real and inverted image will be formed 40 cm in front of the mirror of same size as object.
(c) Virtual, erect and enlarged image will be formed 40 cm behind the mirror.
(d) Virtual and erect image will be formed 40 cm behind the mirror of same size as object.

(E) The magnification produced by a concave mirror when object is placed between Pole and Focus is:
(a) m = +1 (b) m = -1
(c) m > +1 (d) m > -1
(c) m > + 1

Explanation: The magnification produced by a mirror is the ratio of height of image to the height of object. As the image formed by a concave mirror when object is placed between pole and focus is virtual, erect and magnified, m > + 1.

Question 9.
While brushing her teeth one morning, Reema noticed that while she was holding the tooth brush in her left hand, it was just the opposite in her image formed by the plane mirror. She was amused but knew why it was so!

What is the name of the phenomenon in which the right side of an object appears to be the left side of the image in a plane mirror?
Lateral inversion is the phenomenon in which the right side of an object appears to be the left side in its image in a plane mirror.

Question 10.
One of the most common uses for the convex mirror is the passenger-side mirror on your car. Convex mirrors are also often found in the hallway of various buildings including hospitals, hotels, schools, stores and apartment buildings.
Usually, these mirrors are mounted to a wall or ceiling at points where hallways cross each other or make a sharp turn. This eliminates blind spots and provides people with a good overview of their surroundings. The convex mirror is also used to provide safety for motorists on roads, driveways and in alleys where there is a lack of visibility.

A convex mirror is also a simple way of improving the safety in your warehouse or production environment. In a work environment or warehouse, convex mirrors can be placed at crossings or blind spots to enable workers to see approaching forklifts, other vehicles or approaching colleagues. This provides your employees with the necessary overview of their work environment and therefore increases the safety in your workplace.

Another use of the convex mirror in this work environment is during the production process, such as on the conveyor belt to view your product from different angles. This can increase the quality of your products by becoming aware of any faults in the production and increase the efficiency of the production process by eliminating the necessity to check your products by picking them up from the conveyor belt.
(A) Select the characteristics of convex mirror due to which it is used as rear view mirrors.
(I) Convex mirror always forms a virtual and erect image
(II) Convex mirrors may form real or virtual image depending upon the position of object
(III) Convex mirrors provide a wider field of view as they are curved outwards.
(IV) Images formed by convex mirrors are usually larger than the object.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (III) and (IV)
(a) Both (I) and (III)

Explanation: Convex mirrors are used as rearview mirrors in cars because they always form virtual and erect image and provide a wider field of view as they are curved outwards.

(B) As the object is moved away from the focus of the convex mirror:
(a) size of image does not change
(b) size of image increase
(c) size of image decreases
(d) cannot be ascertained as size of image depends upon the focal length of the convex mirror.

(C) The magnification produced by a convex mirror is always:
(a) Equal to +1
(b) Equal to -1
(c) Greater than +1
(d) Smaller than +1

(D) The image formed by a convex mirror of focal length 30 cm is a quarter of the object. The object distance and image distance, along with the sign convention, are tabulated below. Select the row containing the correct values of object and image distance:

 Object Distance (u) Image Distance (v) (a) – 90 cm + 22.5 cm (b) – 22.5 cm + 90 cm (c) – 90 cm – 22.5 cm (d) – 90 cm + 90 cm

(a) Object Distance : -90 cm ; Image Distance: +22.5cm

Explanation: it is given that focal Length, f = + 30 cm and size of image = VA times size of object.

(E) Consider an object 7.0 cm in length which is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. The size and position of image formed is:
(a) size of image = -3 cm, position of image = + $$\frac{60}{7}$$ cm
(b) size of image = +3 cm, position of image = + $$\frac{60}{7}$$ cm
(c) size of image = +3 cm, position of image = + $$\frac{7}{60}$$ cm
(d) size of image = -3 cm, position of image = + $$\frac{7}{60}$$ cm
(b) size of image = + 3 cm, position of image = + $$\frac{60}{7}$$ cm

Explanation: Here, height of object = h1 = 7 cm; u = – 20 cm, f= + 30/2cm = + 15cm.
Applying the mirror formula, we get.

Question 11.
When we look down into a pool of water from above, the pool looks less deep than it really is. Similarly, an object kept at the bottom of a pond or pool of water appears to be raised.

This great blue heron finally catches a meal after seeking the waters. To be a successful hunter, the heron must use the refraction principle to determine where the fish are located before making a strike. The heron can accurately determine where to strike by recognizing that the fish are located at a spot that is different from what its eyes tell it.

(A) The apparent depth of the fish in water
(a) Less than the actuaL depth because Light travels from a rarer medium to denser medium.
(b) Less than the actuaL depth because Light travels from a denser medium to rarer medium.
(c) More than the actual. depth because of total internat reflection of Light.
(d) More than the actual depth because Light travels from a denser medium to rarer medium.
(b) Less than the actual depth because light travels from a denser medium to rarer medium.

Explanation: As light travels from a denser medium (water) to a rarer medium (air), the light rays undergo refraction and bend away from the normal. To an observer, the position of fish in water appears to be raised as shown in the figure above. Therefore, the apparent depth of the fish in water is less than the actual depth due to refraction of light.

(B) A student was thinking what would happen if the medium is changed from water (refractive index of water = 1.33) to a new medium A having refractive index 1.5. He listed all possibilities in a tabular form.

Select the row containing the correct observation and reason.

 Observation Reason (a) Speed of light will be more in the new medium A Speed of light in a medium is directly proportional to the refractive index of the medium. (b) Light rays will bend more in water as compared to A Bending of light is more in a rarer medium as compared to a denser medium (c) Apparent depth of fish will be more in water as compared to medium A Light rays will bend when coming from medium A. (d) Apparent depth of fish will be less in water as compared to medium Light rays will bend less when coming from medium A.

(c) Observation – Apparent depth of fish will be more in water as compared to medium A;
Reason: Light rays will bend when coming from medium A.

Explanation: When the fish is kept in medium A, light rays will bend more as compared to water because of which fish will appear to be raised more in A as compared to water.

(C) Select the incorrect statement from the statements below regarding refractive index of a medium:
(a) The refractive index can be (inked to the relative speed of propagation of
tight in different media.
(b) Light propagates with different speeds in different media.
(c) Refractive index of air is approximately equal to 1 as speed of tight is fastest In vacuum.
(d) The refractive index of glass is less than that of water as speed of tight in glass is 2 × 108 m/s and in water is 2.25 × 108 m/s.

(D) Which of the following are not examples of the phenomena of refraction of light?
(I) Spectacles worn by people to correct their defect of vision
(II) Formation of rainbow
(III) Solar furnaces
(IV) SatelLite dishes
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (II) and (IV)
(c) Both (III) and (IV)

Explanation: Solar furnaces and satellite dishes use parabolic or concave mirrors and make use of the phenomenon of reflection of light, whereas spectacles worn by people having defective vision and formation of rainbow are based on the phenomenon of refraction of light.

(E) A ray of light continues moving along the same path while passing through air- water interface. The angle of refraction for the ray is:
(a) 0°
(b) 45°
(c) 90°
(d) Greater than 90°

Question 12.
Sumati wanted to see the stars of the night sky. She knows that she needs a telescope to see those distant stars. She finds out that the telescopes, which are made of lenses, are called refracting telescopes and the ones which are made of mirrors are called reflecting telescopes.

So, she decided to make a refracting telescope. She bought two lenses, L1 and L2 out of which L1 was bigger and L2 was smaller. The larger lens gathers and bends the light, while the smaller lens magnifies the image. Big, thick lenses are more powerful. So to see far away, she needed a big powerful lens. Unfortunately, she realized that a big lens is very heavy.

Heavy lenses are hard to make and difficult to hold in the right place. Also since the light is passing through the lens, the surface of the lens has to be extremely smooth. Any flaws in the lens will change the image. It would be like looking through a dirty window.
(A) Based on the diagram shown, what kind of lenses would Sumati need to make the telescope?
(a) Concave lenses
(b) Convex lenses
(c) Bifocal lenses
(d) Flat lenses
(a) Concave lenses

(B) If the powers of the lenses L1 and L2 are in the ratio of 4 : 1, what would be the ratio of the focal length of L1 and L2?
(a) 4 :1
(b) 1: 4
(c) 2:1
(d) 1:1

(C) What is the formula for magnification obtained with a lens?
(a) Ratio of height of image to height of object
(b) Double the focal length
(c) Inverse of the radius of curvature
(d) Inverse of the object distance

(D) Sumati did some preliminary experiment with the lenses and found out that the magnification of the eyepiece (L2) is 3. If in her experiment with L2 she found an image at 24 cm from the lens, at what distance did she put the object?
(a) 72 cm
(b) 12 cm
(c) 8 cm
(d) 6 cm
(c) 8 cm

(E) Sumati bought not-so-thick lenses for the telescope and polished them. What advantages, if any, would she have with her choice of lenses?
(a) She will not have any advantage as even thicker lenses would give clearer images.
(b) Thicker lenses would have made the telescope easier to handle.
(c) Not-so-thick lenses would not make the telescope very heavy and also allow considerable amount of light to pass through them.
(d) Not-so-thick lenses will give her more magnification.
(c) Not-so-thick lenses would not make the telescope very heavy and they will also allow considerable amount of light to pass through them.

Question 1.
Which type of mirror should a student use if he wants to project the image of a candle flame on the walls of the school laboratory?

Question 2.
If a magnification of -1 is to be obtained using a concave mirror of focal length 6 cm, then what should be the position of the object?
Magnification of -1 means that the image is real and size of image is equal to the size of the object. This is possible when the object is placed at C of a concave mirror. Therefore, position of object = C = 2f = 12 cm in front of the concave mirror.

Question 3.
A man stands 10 m away in front of a large plane mirror. How far must he walk before he is 5 m away from his image?
As the distance between the man and the mirror is 10 m, the distance between man and his image is 10 + 10 or 20 m, as image distance and object distance are equal. Distance between the man and his image is 5 m when the man is 2.5 m away from the mirror. Therefore, the man has to walk 10 m- 2.5m = 7.5 m towards the mirror.

Question 4.
Find the focal length of a convex mirror whose radius of curvature is 32 cm.

Question 5.
Observe the given figure. What is the angle of reflection?

The angle of reflection is the angle between the normal and the reflected ray.
Therefore: 900 70° = 200

Question 6.
An object O is placed in front of a plane mirror as shown beLow.

At which point is the image of the object ‘O’ formed?
At point R, the image of object ‘O’ is formed.

Question 7.
Define power of a lens.

Question 8.
Both a spherical mirror and a thin spherical lens have a focal length of (-) 15 cm. What type of mirror and lens are these?
Both are concave
Alternative answer that should be given credit: Plano-concave lens

Explanation: Focal length of a concave mirror is the distnace of principal focus F of the mirror from the pole P of the mirror. In concave lens – Focal length is the distnace of principal focus of the lens from the optical centre C. All the distances parallel to the principal axis of the spherical mirror, are measured from the pole of the mirror and in lens this distance is measured from the optical centre of the lens.

In mirror or lens the distances measured in a direction opposite to the direction of incident light are taken as negative.

Concave mirror:

Concave lens:

Question 9.
The image formed by a concave mirror is observed to be real, inverted and larger than the object. Where is the object placed?
Between the principal focus and the centre of curvature.

Explanation: In figure, object AB is placed between F and C of a concave mirror MN in a direction perpendicular to the principal axis of the mirror. A ray of the light starting from A falls on the mirror along AD parallel to the principal axis. On reflection at D, it passes through F. Another ray of light starting A and falling on the mirror along AE passes through centre of curveture C. On reflection at E, it retraces its path. The two reflected rays, DFA’ and EAC. meet at A’. Draw A’B’ perpendicular to the principal axis of the mirror. Therefore A’B1 is the image of mirror which is formed beyond C and is real, inverted and larger in size than the object.

Question 10.
Name the part of a lens through which a ray of light passes without suffering any deviation.

## Online Education for Class 10 Science MCQs Multiple Choice Questions with Answers

### MCQ Questions for Class 10 Science Physics with Answers

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## MCQ Questions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current with Answers

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## Magnetic Effects of Electric Current Class 10 MCQs Questions with Answers

Magnetic Effect Of Electric Current Class 10 MCQ Question 1.
If the key in the arrangement as shown below is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are:

(a) Concentric circles
(b) Elliptical in shape
(c) Straight lines parallel to each other
(d) Concentric circles near the point O but of elliptical shapes as we go away from it
(c) Straight lines parallel to each other

Explanation: If the circuit connection breaks by taking the key out, then no current will flow through the wire and no magnetic field will exist due to the conductor.

Therefore, at the point O, there will be only Earth’s magnetic field and they are straight lines parallel to each other.

Magnetic Effect Of Electric Current MCQ Question 2.
A current-carrying conductor is held in exactly vertical direction. In order to produce a clockwise magnetic field around the conductor, the current should passed in the conductor:
(a) from top towards bottom
(b) from left towards right
(c) from bottom towards top
(d) from right towards left

Class 10 Magnetic Effect Of Electric Current MCQ Question 3.
A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is on. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anticlockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to:

(a) A
(b) B
(c) A if the current is small and B if the current is large
(d) B if the current is small and A if the current is large

MCQ On Magnetic Effect Of Electric Current Question 4.
A uniform magnetic field exists in the plane of paper pointing from left to right as shown in the figure. In the field, an electron and a proton move as shown. The electron and the proton experience:

(a) forces both pointing into the plane of paper
(b) forces both pointing out of the plane of paper
(c) forces pointing into the plane of paper and out of the plane of paper, respectively
(d) forces pointing opposite and along the direction of the uniform magnetic field respectively
(a) forces both pointing into the plane of paper

Explanation: Apply Fleming’s left hand rule and considering that the flow of current in the direction of the movement of proton and in the direction opposite to the flow of electrons. So, the current due to both electron and proton will be in the same direction because of which, the forces acting on both will be in the same direction. By Fleming’s Left hand rule, the direction of force is pointing into the plane of paper.

Magnetic Effects Of Electric Current Class 10 MCQ Question 5.
For a current in a long straight solenoid N and S-poles are created at the two ends. Among the following statements, the incorrect statement is:
(a) The field lines inside the solenoid are in the form of straight lines, which indicates that the magnetic field is the same at all points inside the solenoid
(b) The strong magnetic field produced inside the solenoid can be used to magnetize a piece of magnetic material Like soft iron, when placed inside the coil
(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet
(d) The N and S-poles exchange position when the direction of current through the solenoid is reversed.

Magnetic Effects Of Electric Current MCQ Question 6.
An electron moves with a speed v along positive direction of the x-axis. If a magnetic field B acts along the positive y-direction, then the force on the electron will act along:
(a) x-axis
(b) y-axis
(c) -ve z-direction
(d) +ve z-direction [Diksha]
(c) -ve z-direction

Explanation: As electron is moving in positive x-direction, then, according to Maxwell’s right-hand thumb rule, the current is moving in negative x-direction and the magnetic field acts on positive y-direction.

Thus, the thumb will be in negative z-direction, which is the direction of force.

MCQ Of Magnetic Effect Of Electric Current Question 7.
Which of the following is not attracted by a magnet:
(a) Steel
(b) Cobalt
(c) Brass
(d) Nickel

Ch 13 Science Class 10 MCQ Question 8.
The magnetic field lines:
(a) intersect at right angles to one another
(b) interest at an angle 45° to each another
(c) do not cross one another
(d) cross at an angle of 60° to one another
(c) do not cross one another

Explanation: The magnetic field lines do not cross one another because the resultant force at any point on the north pole can only be in one direction. This is impossible if the Lines intersect

Related Theory
If two magnetic field lines are found to cross each their, it means that at the point of intersection, the compass needle would point towards two directions. which is not possible.

Magnetism Class 10 MCQ Question 9.
The magnetic field inside a long straight solenoid carrying current is
(a) uneven
(b) zero
(c) same at aLL points
(d) different at aU Points
(c) same at all points

Explanation: The magnetic field lines inside a long straight solenoid carrying current is in the form of parallel straight tines which indicates that the magnetic field is some at oIL points inside the solenoid.

MCQs On Magnetic Effects Of Electric Current Class 10 Question 10.
To convert an AC generator into DC generator:
(a) Split ring type commutator must be used
(b) SLIp rings and brushes must be used
(c) A stronger magnetic fieLd has to be used
(d) A rectangular wire Loop has to be used

Magnetic Effect Of Electric Current MCQs Question 11.
The most important safety method used for protecting home appliances from short-circuiting or overloading is:
(a) Earthing
(b) Use of fuse
(c) Use of stabiLizers
(d) Use of electric meter

Class 10 Science Ch 13 MCQ Question 12.
Which of the given statements are incorrect regarding magnetic field Unes?
(I) The direction of magnetic field at a point is taken to be the direction In which the south pole of a magnetic compass needle points.
(II) Magnetic field Lines are closed curves.
(III) If magnetic field Lines are parallel and equidistant, they represent zero-field strength.
(IV)Relative strength of magnetic field is shown by the degree of closeness of the field lines.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (III)
(d) Both (II) and (IV)
(c) Both (I) and (III)

Explanation: The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points. If magnetic field lines are parallel and equidistant, they represent uniform field strength.

MCQ Questions On Magnetic Effects Of Electric Current Question 13.
The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly.
Select the correct observations:
(I) The maximum deflection of the galvanometer will be observed when the magnet was moving out of the solenoid.
(II) The maximum deflection of the galvanometer will be observed when the magnet was moving slowly into of the solenoid.
(III) The minimum deflection of the galvanometer will be observed when the magnet was at rest inside the solenoid.
(IV) The minimum deflection of the galvanometer will be observed when the magnet was moving towards the solenoid.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
(a) Both (I) and (III)

Explanation: The maximum deflection of the galvanometer will be observed when the magnet was moving out of the solenoid as maximum current is induced in the coil due to the relative motion between the solenoid coil and the magnet. Whereas, the minimum deflection of the galvanometer will be observed when the magnet was at rest inside the solenoid as no current is induced in the coil.

MCQs On Magnetic Effect Of Electric Current Question 14.
A student places some iron fillings around a magnet. The iron fillings arrange themselves as shown in image below.

Four points labelled A, B, C and D have been marked in the figure.
Select the correct statement regarding the strength of magnetic field at these points:
(I) The magnetic field will be strongest at A.
(II) The magnetic field will be strongest at B.
(III) The magnetic field will be weakest at C.
(IV)The magnetic field will be weakest at D.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)

MCQ Of Magnetic Effect Of Electric Current Class 10 Question 15.
The figure below shows an electric generator.

The coil ABCD is rotated and the direction of induced current is noted initially and when coil completes half cycle of the rotation.
Select the row containing correct direction of induced current in the coil ABCD.

(a) Initially when coil ABCD is rotated ABCD; when coil complete is half cycle of rotation DCBA

Explanation: Length AB of the coil ABCD is moving upwards and the magnetic field acts from left to right. Hence, according to Fleming’s right-hand rule, the direction of induced current will be from A to B. And the direction of induced current in the length CD will be from C to D. The direction of current in the coil is ABCD. After half a rotation, length AB starts moving down whereas length CD starts moving upward. The direction of the induced current in the coil gets reversed as DCBA.

Question 16.
Study the graphs (A) and (B) shown below and select the row containing incorrect information from the table.

Question 17.
The magnetic field lines inside a current-carrying solenoid are in the form of parallel straight lines which indicate that:
(a) The magnetic field is zero inside the solenoid.
(b) The field is uniform inside the solenoid.
(d) The field is non-uniform inside the solenoid.
(d) The field is very strong inside the solenoid.
(b) The field is uniform inside the solenoid.

Explanation: The magnetic field lines inside a current-carrying solenoid are in the form of parallel straight lines which indicate that the field is uniform inside the solenoid.

Question 18.
A current-carrying conductor is held in the vertical direction. In order to produce a clockwise magnetic field around the conductor, the current should be passed in the conductor:
(a) From top to bottom
(b) From left to right
(c) From bottom to top
(d) From right to left
(a) From top to bottom

Explanation: By applying right-hand thumb rule, we note that in order to produce a clockwise magnetic field around the conductor, the current should be passed from top to bottom in the conductor as shown:

Question 19.
An induced emf is produced when a magnet is moved into a coil. The magnitude of induced emf does not depend on:
(a) The number of turns of the coil
(b) The speed with which the magnet is moved
(c) The strength of the magnet
(d) The resistivity of the wire of the coil

Question 20.
Imagine that a negative charge is moving towards a person. The direction of magnetic field lines will be in:
(a) Clockwise direction
(b) Anticlockwise direction
(c) Vertically upward direction
(d) Vertically downward direction

### Assertion Reasoning questions Class 10 Science Chapter 13

For the following questions, two statements are given one labeled Assertion (A) and the other labeled Reason (R). Select the correct Answer to these questions from the codes (a), (b), (c), and (d) as given below.
(a) Both (A) and (R) are true, and (R) is correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is flase, but R is true.

Question 21.
Assertion (A): The energy of charged particle moving in a uniform magnetic field does not change.
Reason (R): Work done by magnetic field on the charge is zero.
(a) Both (A) and (R) are true and (R) is the correct explanation of assertion.

Question 22.
Assertion (A): The compass placed near the current-carrying wire remains stationary.
Reason (R): The current flowing through a wire gives rise to a magnetic field.
(d) (A) is wrong but (R) is correct.

Explanation: The compass when placed near the current-carrying wire gets deflected because the current flowing through the wire gives rise to a magnetic field.

Question 23.
Assertion (A): The direction of force acting on a current carrying conductor placed in a magnetic field gets reversed on reversing the direction of current flowing through the conductor.
Reason (R): Magnitude of force is highest when direction of current is parallel to direction of magnetic field.

Question 24.
Assertion (A): Current can be induced in a coil by changing the magnetic field around it.
Reason (R): A galvanometer connected to a coil can deflect either to the left or right of the zero marks.
(b) Both (A) and (R) are true but (R) is not the correct explanation of assertion. Explanation: Voltage and hence current is induced in a coil due to a changing magnetic field and this process is known as electromagnetic induction.

A galvanometer is a device that detects the presence of current by deflecting the needle to one side of the zero mark, but this does not explain the current induced in the coil.

Competency-Based Questions (CBQs)

Question 1.
The space surrounding a magnet in which magnetic force is exerted, is called a magnetic field. The direction of magnetic field lines at a place can be determined by using a compass needle. A compass needle placed near a magnet gets deflected due to the magnetic force exerted by the magnet.

The north end of the needle of the compass indicates the direction of magnetic field at the point where it is placed. When the magnet shown in the diagram below is moving towards the coil, the galvanometer gives a reading to the right.

(A) What is the name of the effect being produced by the moving magnet?
(B) State what happens to the needle shown on the galvanometer when the magnet is moving away from the coil.
(C) If the magnet is moved towards the coil at a great speed, state two changes that you would notice in the galvanometer.
(D) List three sources of magnetic fields.

Question 2.
Happy’s friend once got a bicycle fitted with a dynamo to school. Happy was quite thrilled to see a cycle fitted with a dynamo and decided to find out more about this. A bottle dynamo or sidewall dynamo is a small electrical generator for bicycles employed to power a bicycle’s lights. When the bicycle is in motion and the dynamo roller is engaged, electricity is generated as the tire spins the roller.Two other dynamo systems used on bicycles are hub dynamos and bottom bracket dynamos.

Fleming’s Right-hand rule gives:
(a) magnitude of the induced current.
(b) magnitude of the magnetic field
(c) direction of the induced current
(d) both, direction and magnitude of the induced current

Question 3.
Vaibhav performed an activity to observe an important breakthrough made by the English Physicist faraday. He took a coil of wire AB having a large number of turns and connected the ends of the coil to a galvanometer. He observed a momentary deflection in the needle of the galvanometer, say to the right, when the North pole of a strong magnet was moved towards the end B of the coil.
(A) Name the phenomenon discovered by Faraday.
The phenomenon was Electromagnetic induction.

(B) Why does Vaibhav observe momentary deflection in the galvanometer?
This is due to induced current in the coil as a result of changing magnetic field associated with the coil.

(C) What happens to the deflection in the galvanometer when the motion of the magnet stops?

(D) What will be observed when the north pole of the magnet is withdrawn away from the coil?
We observe that the galvanometer is deflected toward the left, showing that the current is now set up in the direction opposite to the first

Question 4.
Transmission lines are sets of wires that carry electric power from generating plants to the substations that deliver power to customers. At a generating plant, electric power is “stepped up” to several thousand volts by a transformer and delivered to the transmission line. When Kumar visited his grandmother’s home, he was quite surprised to see the transmission lines going right above their colony!

A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in the figure. The direction of a magnetic field at a point will be north to south:

(a) directly above the wire
(b) directly below the wire
(c) at a point located in the plane of the paper on the north side of the wire
(d) at a point located in the plane of the paper on the south side of the wire
(b) directly below the wire

Explanation: If we observe the direction of the magnetic field by applying the right hand thumb rule, then we will find that the directior of the magnetic field is from north to south below the wire

Question 5.
Fix a sheet of white paper on a drawing board using some adhesive material. Place a bar magnet in the centre of it. Sprinkle some iron filings uniformly around the bar magnet as shown in figure below. Now tap the board gently.

In the next activity, take a small compass and a bar magnet. Place the magnet on a sheet of white paper fixed on a drawing board, using some adhesive material. Mark the boundary of the magnet. Place the compass near the north pole of the magnet. Mark the position of two ends of the needle. Now move the needle to a new position such that its south pole occupies the position previously occupied by its north pole. In this way, proceed step by step till you reach the south pole of the magnet as shown in Fig. below.

Join the points marked on the paper by a smooth curve. Repeat the above procedure and draw as many lines as you can. Observe the deflection in the compass needle as you move it along a field line.
(A) Select the correct observations and conclusions when cardboard is gently tapped in the first activity:
(I) The iron filings arrange themselves in a pattern.
(II) The magnet experiences a force as the iron atoms exert its influence on it.
(III) The force experienced by the magnet makes iron filings to arrange in a pattern.
(IV) The region surrounding a magnet, in which the force of the magnet can be detected, is said to have a magnetic field.
(a) Both (I) and (II)
(b) Both (III) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)

(B) The lines along which the iron filings align themselves represent:
(a) Magnetic field lines.
(b) Electric field lines
(c) Magnetic potential
(d) Electric potential
(a) Magnetic field lines

Explanation: The magnetic field lines are the imaginary lines drawn around a magnet that represent the m etic field around a magnet.

(C) Select the row containing the correct observation when a small compass is placed near the bar magnet in the second activity:

 North Pole of Compass Needle South Pole of Compass Needle (a) It points towards the North pole of the magnet It points towards the South pole of the magnet (b) It points towards the North pole of the magnet It points away from the North pole of the magnet (c) It points away from the South pole of the magnet It points away from the North pole of the magnet (d) It points away from the North pole of the magnet It points towards the North pole of the magnet

(d) North Pole of compass needle: It points away from the North Pole of the magnet: South Pole Compass needle: it Points towards the North Pole of the Magnet.

Explanation: The small compass is actuaLly a magnetic compass needle. Its North pole points away from the North pole of the bar magnet and its South pole points towards the North pole of the bar magnet as like poles repel each other and unlike poles attract each other.

(D) When the compass needle is moved along a field line, the deflection in the compass:
(a) First increases and then decreases.
(b) Increases as the needle is moved towards the poles.
(c) Decreases as the needle is moved towards the poles.
(d) Remains constant
(E) Given below are four figures showing the direction of magnetic field lines around a bar magnet. Select the option showing the correct direction:

Question 6.
Vikram had gone to his cousin’s apartments to celebrate holi. While climbing the stairs he observed that all the electric meters and main switches were installed on one side of the stair case. On each meter box, apart from other information, the following was also written: kWh meter, 220VAC.

How many times does AC used in India change direction in one second?
The frequency of alternating current in India is 50 Hertz. This means that the AC changes current every 1/100 second.

Question 7.
Kritika once observed a caling bell on the wall just outside the principal’s room. Although she knew its purpose, she wanted to know the construction and working of an electric calling bell, which is a mechanical or electronic bell that functions by means of an electromagnet.

(a) Will decrease
(b) Will increase
(c) Will become zero
(d) Will remain the same

Question 8.
Take a coil of wire AB having a large number of turns. Connect the ends of the coil to a galvanometer as shown in Fig. (a) below.

(a)
Take a strong bar magnet and move its north pole towards the end B of the coil. Observe the deflection in the galvanometer towards right. Now withdraw the north pole of the magnet away from the coil. Next, place the magnet stationary at a point near to the coil, keeping its north pole towards the end B of the coil. First move the coil towards the north pole of the magnet and then away from the magnet. Observe the deflection of the galvanometer in both cases.

Next, take two different coils of copper wire having large number of turns (say 50 and 100 turns respectively). Insert them over a non-conducting cylindrical roll, as shown in Fig. below. Connect the coil-1, having larger number of turns, in series with a battery and a plug key. Also connect the other coil-2 with a galvanometer as shown in fig. (b) below.

Plug in the key. Observe the deflection in galvanometer. Next, disconnect coil-1 from the battery. Note your observations.
(A) Select the correct observations when a strong bar magnet is taken and its north pole is moved near the coil in the first activity:
(I) There is a momentary deflection in the needle of the galvanometer, say to the right, when the north pole of a strong bar magnet is moved towards the end B of the coil.
(II) Momentary deflection in the galvanometer needle indicates the presence of a force in the coil AB.
(III) The deflection in the galvanometer increases the moment the motion of the magnet stops.
(IV) When the north pole of the magnet is withdrawn away from the coil, the galvanometer is deflected toward the left.
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (III) and (IV)
(b) Both (I) and (IV)

Explanation: Momentary deflection in the galvanometer needle indicates the presence of a current in the coil AB. The deflection in the galvanometer becomes zero the moment the motionof the magnet stops as no current is induced in the coil now.

(B) Refer to fig. (a) above. Place the magnet stationary at a point near to the coil, keeping its north pole towards the end
B of the coil.
Select the row containing incorrect observation:

 Movement of coil Deflection of the galvanometer needle (a) Coil is moved towards the North pole of the magnet Towards right (b) Coil is moved away the North pole of the magnet Towards left (c) Both coil and magnet are stationary Momentary deflection (d) Both coil and magnet are stationary No deflection

(c) Movement of coil: Both coil and magnet are stationary; Deflection of galvanometer needle: Momentary deflection

Explanation: When the coil is moved towards the north pole of the galvanometer, the galvanometer needle deflects towards right and when the coil is moved away from the north pole of the magnet, the galvanometer needle deflects in the opposite direction towards right. This is because the induced current is now set up in the direction opposite to the first.

However, when both the coil and magnet are stationary, there is no induced current in the coil and hence no deflection in the needle of the galvanometer.

(C) In the first activity, what would be observed if the south pole of the magnet was moved away from the end B of the
coil?
(a) Deflection in same direction as when north pole was moved towards end B of the coil, i.e., towards right.
(b) Deflection in opposite direction as when north pole was moved towards end B of the coil, i.e., towards left.
(c) First deflection towards right and then towards left.
(d) No deflection in galvanometer needle.
(a) Deflection in same direction as when north pole was moved towards end B of the coil, i.e., towards right.

Explanation: When the south pole of magnet is moved away from the end B of the coil, the current will be induced in the coil in the same direction as north pole moving towards the end B of the magnet. Therefore, deflection of galvanometer needle will be in the same direction which is towards right.

(D) Select the incorrect observation when the key is plugged “in” in the second activity:
(a) The needle of the galvanometer instantly jumps to one side and quickly returns to zero, indicating a momentary current in coil-2.
(b) When the battery is disconnected from the coil, there is a momentary deflection of the galvanometer needle in opposite side.
(c) The needle of the galvanometer jumps to one side till the key is plugged “in” indicating that current is induced in coil-2.
(d) As soon as the current in coil-1 reaches either a steady value or zero, the galvanometer in coil-2 shows no deflection.

(E) Cause of induced current in coil 2 in fig (b) is:
(a) Change in magnetic field lines associated with the secondary coil.
(b) Change in magnetic field lines associated with the primary coil.
(c) Change in magnetic force associated with the secondary coil.
(d) Change in magnetic force associated with the primary coil.

Question 9.
Paras was keenly observing the electrician connecting the new electric cooler at their home. He observed that apart from the two wires, there was a third wire which he connected at the plug, which was a three pin plug. He came to know the third wire is the earth wire.

The earth wire is used as a safety measure to:
(b) Prevent shortcircuiting
(c) Prevent electric shock
(d) Voltage fluctuations

Question 10.
When the mason working at Smriti’s house, turned on his tile cutter connected to the switchboard of the living room, there was a fire in the plug. Immediately, her father switched off the electric mains supply and the fire was prevented from spreading further.

State the possible reason for such a situation leading to an electric fire.
One possible reason for this kind of electric fire is that the power rating of the tile cutter was higher than the current carrying limit of the electric circuit to which it was connected. This led to the damaging of the insulation of the connecting wires and hence short circuiting took place.

Question 11.
Valves are mechanical devices designed to control the flow of liquid and gases. Many valves are manually operated. Electrically operated valves are known as solenoid valves. A solenoid valve consists of two basic units: an assembly of the solenoid (the electromagnet) and plunger (the core), and a valve containing an opening (orifice) in which a disc or plug is positioned to control the flow of fluid. The valve is opened or closed by the movement of the magnetic plunger. When the coil is energized, the plunger is drawn into the solenoid (electromagnet) and flow through the orifice is allowed. The valve returns automatically to its original position when current ceases due to the pressure of spring and flow through the orifice is restricted.

(A) Which of the following statements is correct regarding solenoid valve?
(a) Solenoid valves are mechanically operated valves.
(b) A solenoid valve is opened or closed by the movement of the magnetic plunger.
(c) Flow through the orifice is allowed when no current flows through the solenoid coil.
(d) Flow through the orifice is restricted when current flows through the solenoid coil.

(B) Select the incorrect statements regarding the magnetic field in a current carrying solenoid as shown above:
(I) The pattern of the magnetic field lines around a current-carrying sole¬noid is similar to the magnetic field around a bar magnet.
(II) One end of the solenoid behaves as a positive charge and the other end behaves as a negative charge.
(III) The field lines inside the solenoid are in the form of curved lines.
(IV) The magnetic field is uniform inside the solenoid.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (I) and (IV)
(b) Both (II) and (III)

Explanation: One end of the solenoid be-haves as a magnetic north pole and the other end behaves as a magnetic south pole. The field lines inside the solenoid are in the form of parallel straight lines.

(C) The figure below shows the lengthwise section of a current carrying solenoid, where indicates that current is entering into the page and indicates that current is emerging out of the page:

The table below gives the identification of the ends A and B of the solenoid as North or South pole and the justification for the answer. Select the row containing the correct identification of the ends A and B and the correct justification:

(d) End A of Solenoid: South Pole; End B of Solenoid: North Pole; Justification: By Right hand thumb rule, magnetic field is from B to A.

Explanation: The direction of magnetic field around a current carrying conductor is found by using Right Hand Thumb rule, which states that “Imagine that you are holding a current-carrying straight Conductor in your right hand such that the thumb points towards the direction of cur-rent. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field”.

We find that the direction of magnetic field is from B to A and as we know that mag-netic field lines originate from North pole and terminate at south pole, we can say that B is North pole and A is South pole.

Explanation: The magnetic field of a sole-noid increases when we insert an iron core because iron is a ferromagnetic material and ferromagnetic materials help in in-creasing the magnetic property.

(D) Where should a magnetic compass be placed in solenoid to get maximum de-flection in the magnetic compass?
(a) Inside the coil
(b) Near the North Pole
(b) Near the South Pole
(d) In the middle, just above the coil
(E) The magnetic field strength of a sole¬noid can be increased by inserting which of the following materials as the core?
(a) Copper
(b) Silver
(c) Iron
(d) Aluminium

Question 12.
When Joy went to his friend’s place to complete the group task, he saw that several appliances were connected to the same electric supply point. He asked his friend to remove some of the appliances immediately.

What is the danger if too many appliances are connected to the same electric socket?
If too many appliances are connected to the same socket, it may lead to overloading due to which the live and neutral wires may come in contact and cause electric fires.

Question 13.
In Bohr’s model of the hydrogen atom, the electron moves in a circular orbit around the proton. The electron passes by a particular point on the loop in a certain time, so we can calculate a current I = Q/t.

through a circular wire. 1/Ve know that a current carrying conductor has a magnetic field associated with it. It is therefore reasonable to conclude that the hydrogen atom produces a magnetic field and interacts with other magnetic fields.

The figure shows the variation of the magnetic field along the axis of a circular loop with distance from the centre.

(A) Select the correct statements regarding magnetic field produced in a hydrogen atom:
(I) Magnetic field is due to the electrostatic force of attraction between its electron and proton.
(li) Magnetic field is produced in a hydrogen atom as it has no neutron in its nucleus.
(lii) Current is produced in a Hydrogen atom as the electron orbits around the proton.
(IV) Magnetic field is produced in hydrogen atom as this is similar to current flowing through a circular
wire.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (I) and (IV)

(B) Observe the graph between magnetic field along the axis of a circular loop with distance from the centre and select the correct option:
(a) The value of B increases exponentially with distance from the centre on either side of the loop.
(b) The value of B increases linearly with distance from the centre on either side of the loop.
(c) The value of B is minimum at the centre and it increases as we go away from the centre on either side of the loop.
(d) The value of B is maximum at the centre and it decreases as we go away from the centre on either side of the loop.
(d) The value ofB is maximum at the centre and it decreases as we go away from the centre on either side of the Loop.

Explanation: As observed from the graph, the magnetic field along the axis of the circular Loop is maximum at z = 0 cm, which is the centre of the circular loop and decreases as we move away from the centre along the axis.

(C) Select the incorrect statement:
The magnetic field produced by a circular coil of n turns carrying current is:
(a) Inversely proportional to the radius of the circular loop.
(b) Directly proportional to the radius of the circular loop.
(c) Directly proportional to the number of turns in the coil.
(d) Directly proportional to the current in the coil.
(a) Inside the loop: Downward; Outside the loop: Upward; Rule Applied: Right Hand Thumb Rule

Explanation: Applying Right hand thumb rule, we find that the direction of magnetic field inside the loop is in downward direction and in upward direction outside the loop.

(D) Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.

(E) The diagram showing the correct direction of the magnetic field lines at point P and Q in the current carrying circular loop is:

Question 14.
Meters, such as those in analog fuel gauges on a car, are common application of magnetic torque on a current-carrying loop. Figure below shows that a meter is very similar in construction to a motor. The torque is proportional to current I. A linear spring exerts a counter-torque that balances the current-produced torque. This makes the needle deflection proportional to I. If an exact proportionality cannot be achieved, the gauge reading can be calibrated.

The graph below gives the variation of force experienced by a current carrying conductor placed in a magnetic field and the magnitude of current.

(A) The graph above shows that the force experienced by a current carrying conductor in a magnetic field is:
(a) uniform.
(b) Increases linearly with current.
(c) Decreases linearly with current
(d) Reverses on reversing direction of current.
(b) Increases Linearly with current.

Explanation: We observe that the graph between force and current is a straight Line which shows that the force experienced by a current carrying conductor placed in a magnetic field increases linearly with the magnitude of current.

(B) The direction of force experienced by the current carrying loop in the above meter is given by:
(a) Right hand thumb rule
(b) Fleming’s Right hand rule
(d) Fleming’s left hand rule

(C) The magnitude of the force is the highest when the angle between the direction of current and the direction of magnetic field is:
(a) 0°
(b) 45°
(c) 90°
(d) 180°

(D) The relation between direction of current and the direction of force acting on a current carrying conductor when it is ptaced in a magnetic fieLd is:
(a) They are perpendicular to each other
(b) They are parallel to each other
(c) They are opposite to each other
(d) Cannot be predicted
(a) They are perpendicular to each other

Explanation: The direction of force acting on a current carrying conductor, direction of current in the conductor and direction of magnetic field are mutually perpendicular to each other.

(E) Crosses x represent a uniform magnetic field directed into the paper. A conductor XY placed in the field carries current in Y to X direction.

The direction of the force experienced by the conductor, direction of force if the direction of field and direction of current both are reversed and name of the rule applied are given below.
Select the row containing the correct directions of force and ruLe appLied.

(c) direction of force experienced by conductor : Downward, Downward; Rule Applied: fleming’s left hand rule.

Explanation: Applying Fleming’s left hand rule, we find that force acts in downward direction. When the direction of both current and magnetic field are reversed, direction of force will still be in downward direction.

Question 15.
DC Motor is a motor which converts DC power into rotary movement and so is the name Direct Current (DC) Motor. It works on the principle of energy conversion i.e. Electrical energy to Mechanical energy. Application of Voltage produces Torque which results in Motion. Internal view of this type of Motor is shown in the Fig. below.

It consists of four main components. They are: Stator, Rotor, Winding and Commutator
Stator: The outside part of a motor is called as Stator. It is composed of two or more permanent magnet pole pieces.
Rotor: The inner part of the motor which rotates is called as rotor. It is composed of armature winding which is connected to the external circuit through commutator. Similar to stator, rotor is also made up of ferromagnetic materials.
Winding: Winding consists of series or parallel connection of coils made of copper. Commutator: A commutator acts as a switch that reverses the direction of current between the rotor and external circuit.
(A) Select the incorrect statements regarding the components of a DC motor:
(I) Stator is the outside part of the motor and is composed of two or more permanent magnet pole pieces.
(II) Rotor is the outer part of the motor which rotates and is composed of armature winding.
(III) Winding consists of only parallel connection of coils made of copper.
(IV) Commutator acts as a switch that reverses the direction of current between the rotor and external circuit.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (I) and (IV)

(B) Refer to the figure (b) above and select the row containing the correct directions of the force acting on arms PQ and RS :

 Direction of Force acting on: PQ RS (a) Upwards Downwards (b) Upwards Upwards (c) Downwards Downwards (d) Downwards Upwards

(C) Which of the following rule is used to determine the direction of rotation of D.C motor?
(b) Lenz’s Law
(c) Fleming’s Right-hand Rule
(d) Fleming’s Left-hand Rule

(D) The role of commutator in DC motors is to:
(a) Reverse the direction of current after every half rotation of the coil.
(b) Reverse the direction of current one complete rotation of the coil.
(c) Maintain the same direction of current after one complete rotation of the coil.
(d) To reverse the direction of magnetic field after every half rotation of the coil.

(E) Which of the following statements is incorrect regarding commercial motors?
The commercial motors use:
(a) An electromagnet in place of a permanent magnet.
(b) A permanent magnet in place of an electromagnet.
(c) Large number of turns of the conducting wire in the current carrying coil.
(d) A soft iron core on which the coil is wound.
(E) (b) A permanent magnet in place of an electromagnet.
Explanation: The commercial motors use an electromagnet in place of permanent magnet. Moreover, the soft iron core, on which the coil is wound, plus the coils, is called an armature. This enhances the power of the motor.

Question 16.
Generators are useful appliances that supply electrical power during a power outage and prevent discontinuity of daily activities or disruption of business operations. Generators have been a must-have item for vigilant business owners and homeowners for decades. And they’ve only grown more popular in recent years, thanks in part to their wide range of functions. Generators are synonymous with disaster preparedness and emergency use is one of their most common jobs. Generators’ usefulness during a natural disaster such as a hurricane or flood that knocks out power for days on end ranges from convenient to downright life-saving.

There are two main types of backup generators: AC (alternating current) and DC (direct current). AC and DC generators both use electromagnetic induction to generate electricity. However, the process they use is different. An AC generator creates an alternating current that periodically reverses direction. But in a DC generator, a direct current flows in one direction.

(A) The rule to determine the direction of induced current in a coil is:
(a) Coulomb’s law
(b) Right hand rule
(c) Fleming’s left hand rule
(d) Fleming’s right hand rule

(B) The following table shows the directions of motion of conductor, magnetic field and current in the Fleming’s right hand rule. Select the row containing the correct combination:

(a) Thumb: Motion of conductor; Forefinger: Magnetic field; Middle or Central Finger: Inducent Current

Explanation: Fleming’s right hand rule states that if you stretch the thumb,forefinger and middle finger of the right handmutually perpendicular to each other such thatthe forefinger gives the direction of magneticfield and the thumb points in the direction of themotion of a conductor then, the middle fingerwill give the direction of the induced current.

(C) Select the incorrect statements regarding electric generator:
(I) In an electric generator, electrostatic energy is used to rotate a conductor in a magnetic field to produce electricity.
(II) Electric generator works on the principle of electromagnetic induction.
(III) Current is induced in a coil when a coil is rotated in an electric field.
(IV) Large current is induced if there are larger numbers of turns in the coil.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) Both (II) and (IV)

(D) The essential difference between an AC generator and a DC generator is that
(a) AC generator has an electromagnet while a DC generator has permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage,
(d) AC generator has slip rings while the DC generator has a commutator.
(d) AC generator has slip rings while the DC generator has a commutator.

Explanation: To get a direct current a split¬ring type commutator must be used. With this arrangement,one brush is at all times in contact with the arm moving up in the field,while the other is in contact with the arm moving down.Thus a unidirectional current is produced and the generatoris called a DC generator. Whereas, in AC generator, two rings are present.

(E) The meaning of the statement “Frequency of AC in India is 50 Hz” is:
(a) The AC changes direction after every 50 s
(b) The AC changes direction after every 100 s
(c) The AC changes direction after every 1/100 s
(d) The AC changes direction after every 1/50 s
(c) The AC changes direction after every 1/100 s.

Explanation: Frequency is the number of complete oscillations in one second. Frequency of 50 Hz means that there are 50 complete oscillations in 1 second. As AC changes direction twice in one oscillation, it changes direction after every 1/100 s.

Question 1.
Define the term induced electric current.
Induced electric current: It is the current which is created due to the relative motion of coil or magnet. The induced current is found to be the highest when the direction of motion of the coil is at right angles to the magnetic field.

Related Theory
Oersted’s experiments showed that a current produces a magnetic field. Faraday discovered that a moving magnet can be used to generate electric currents.
Induced current is not like the one due to an electric cell.
In an electric cell, the chemical energy is converted into electric energy.
The phenomenon of generation of an electric current in a circuit from magnetic effects is called electro-magnetic induction.

Question 2.
The change in magnetic field lines in a coil is the cause of induced electric current in it. Name the underlying phenomenon.

Question 3.
What is the function of a galvanometer in a circuit?
Galvanometer is an electromechanical instrument used to detect or indicate the presence of current by deflection in a circuit.
It consists of a pointer which can move along a scale with zero marked at its centre and is attached to a moving coil.

Related Theory
Depending on the direction of induced current given by Flemings, Right Fiand rule, the pointer of galvanometer can deflect to the right or left of the zero mark of the scale.

If no current is induced, the pointer remains at the centre of the scale, which reads 0.

Question 4.
Why does a compass needle get deflected when brought near a bar magnet?
The needle of a compass is a small magnet. When a compass needle is brought near a bar magnet, its magnetic field lines interact with that of the bar magnet and therefore the compass needle gets deflected.

Question 5.
A straight wire carrying electric current is moving out of a plane of paper and is perpendicular to it. What is the direction of the magnetic field?

Question 6.
What happens when an iron core is inserted into a current carrying solenoid?
When an iron core is inserted into a current carrying solenoid, strength of the magnetic field produced inside the solenoid increases and it forms an electromagnet.

Question 7.
Under what condition does a current carrying conductor kept in a magnetic field experience maximum force?

Question 8.
What is indicated by crowding of magnetic field lines in a given region?
The crowding of magnetic field lines in a given region indicates that the magnetic field is stronger in that region.

Question 9.
Why is current induced in the secondary coil when current is changed in the primary coil?

## MCQ Questions for Class 10 Science Chapter 16 Management of Natural Resources with Answers

Students can also read MCQ Questions for Class 10 Science Chapter 16 Management of Natural Resources Questions with Answers hope will definitely help for your board exams. https://ncertmcq.com/mcq-questions-for-class-10-science-with-answers/

## Management of Natural Resources Class 10 MCQs Questions with Answers

Management Of Natural Resources Class 10 MCQ Question 1.
Which one of the following is responsible for the ……………… water?
(a) Loss of vegetation cover
(b) Diversion for high water demanding crops
(c) Pollution from urban wastes
(d) Afforestation

Class 10 Science Chapter 16 MCQ Question 2.
Which of the following are water-intensive crops?
(a) Wheat and rice
(b) Wheat and sugarcane
(c) Sugarcane and rice
(d) Wheat and gram
(c) Sugarcane and rice.

Related Theory:
The construction of large dams leads to some problems.
People close to the source grow water-intensive crops like sugarcane and rice whereas people farther downstream do not get sufficient water to grow these crops. This causes social problems resulting due to unequal distribution of water. Other problems related to the construction of dams are economic and environmental problems.

Class 10 Science Chapter 16 MCQ With Answers Question 3.
Consider the following criticisms that are generally addressed when a new project is launched:
(I) Displacement of peasants and local tribals without compensation.
(II) Swallowing up large amount of public money without any benefits.
(Ill) Deforestation and loss of biodiversity. The criticisms about large dams in particular are:
(a) (I) and (II)
(b) (II) and (III)
(c) (I) and (III)
(d) (I), (II) and (III)

Natural Resources Class 10 MCQ Question 4.
The Reni village of Garhwal is famous for:
(a) Monoculturesofpine,teakand eucalyptus.
(b) Chipko Movement.
(c) Extensive biodiversity.
(d) Participation of local people inefficient management of forests.

Sustainable Management Of Natural Resources Class 10 MCQ Question 5.
Which one of the following stakeholders of forests causes the maximum damage to forest?
(a) People who live in or around the forest
(b) The forest department of the government
(c) The wildlife and native enthusiasts
(d) The industrialists
(d) The Industrialist

Ch 16 Science Class 10 MCQ Question 6.
Several factories were pouring their wastes in rivers A and B. Water samples were collected from these two rivers. It was observed that sample collected from river A was acidic while that of river B was basic. The factories located near A and B are:
(a) Soaps and detergents factories near A and alcohol distillery near B.
(b) Soaps and detergents factories near B and alcohol distillery near A.
(c) Lead storage battery manufacturing factories near A and soaps and detergents factories near B.
(d) Lead storage battery manufacturing factories near B and soaps and detergents factories near A.

Chapter 16 Science Class 10 MCQ Question 7.
A diagram of traditional water harvesting system is given below:
The statement which defines the system and its parts is:

(a) This is an ideal setting of the Khadin system and A = Catchment area; B = Saline area and C = Shallow dug well:
(b) This is an ideal setting of the Shallow dug well system and A = Catchment area; B = Saline area and C = Khadin.
(c) This is an ideal setting of Catchment area and A = Khadin, B = Saline area, and C = Shallow dug well.
(d) This is showing the Saline area and A = Catchment area; B = Khadin and C = Shallow dug well.
(a) This is an ideal setting of the Khadin system and:
A = catchment area
B = Saline area
C = Shallow dug well

Explanation: Khadin is a traditional rainwater haversting system in Rajasthan. The main feature of Khadin system of rainwater harvesting is a very long earthen embankment called ‘bund’ built across the lower edge of the sloping farmland. The rainwater from catchment area flows down the slopes and stopped by the bund to form a reservoir the excess water flows through pathwalls (made for this purpose) and filLs the shallow well dug behind the bund. This area is subsequently used for growing crops.

Management Of Natural Resources Class 10 MCQ Questions And Answers Question 8.
The major ill effect of monoculture practice in forests is on the:
(a) biodiversity which faces large destruction
(b) local people whose basic needs can no longer be met from such forests
(c) industries
(d) forest department

Sustainable Management Of Natural Resources Class 10 MCQ With Answers Question 9.
Which of the following are not responsible for failure to sustain water availability underground:
(I) Afforestation
(II) Loss of vegetation cover
(III) Diversion for high water demanding crops
(IV) Pollution from industrial effluents and urban wastes.
(a) Only (I)
(b) Only (II)
(c) Both (I) and (III)
(d) Both (II) and (IV)

MCQ Questions For Class 10 Science Chapter 16 Question 10.
Which among the following factors help in confirming the contamination of river water?
(I) Measurement of pH of river water
(II) Existence of diverse life forms in river water
(III) Presence of chlorine in river water
(IV) Presence of coliform bacteria in river water
Choose the correct option from the following:
(a) (I) and (III)
(b) (II) and (III)
(c) (I) and (IV)
(d) (II) and (IV)

Management Of Natural Resources MCQ Question 11.
Choose the correct statements among the following that are a consequence of raising the height of dams
(I) Deforestation and the loss of biological diversity.
(II) Displacement of large number of peasantsand tribals without adequate compensation or rehabilitation
(III) Loss of valuable agricultural land.
(IV) Generation of permanent employment for local people
(a) Both (I) and (II)
(b) Both (II) and (IV)
(c) (I), (II) and (III)
(d) (I), (III) and (IV)

MCQ On Management Of Natural Resources Class 10 Question 12.
Which of these practices can be adopted to save the environment?
(a) Refuse the use of single-use plastic bags
(b) Reduce the use of paper bags
(c) Recycle single-use bags
(d) Reuse waste food
(a) Refuse the use of single-use plastic bags Explanation: The 5R’s to save the environment are: Refuse, Reduce, Reuse, repurpose and Recycle. The best way to save the environment is by refusing to use products that may harm the environment.

MCQ Questions For Class 10 Science Management Of Natural Resources Question 13.
How does switching off unnecessary electrical appliances help the environment?
(a) It generates electricity when switched off
(b) It reduces wastage of energy
(c) It recycles the amount of energy used
(d) It increases the efficiency of the electrical appliances

MCQ On Management Of Natural Resources Question 14.
Which of these is an example of sustainable development in order to conserve natural resources for the future generation?
(a) Cleaning water resources
(c) Clearing forests to set up new industries
(d) Planning for safe disposal of wastes after mining

Class 10 Management Of Natural Resources MCQ Question 15.
Which of the following industries would be identified as a stakeholder involved in a forest?
(a) That manufacture ceramic products using clay
(b) That make papers using wood products
(c) That make clothes using synthetic materials
(d) That manufacture device that generate electricity using solar energy

Class 10 Science Ch 16 MCQ Question 16.
Which of the following practices will help to conserve the forest?
(a) Deforestation
(b) Banning deforestation
(c) Increased use of firewood by local people
(d) Increased use of timber by industries

MCQ On Sustainable Management Of Natural Resources Question 17.
Which of these explains the use of dams?
(a) To replenish underground water resources
(b) To produce steady supply of water in hilly regions
(c) To provide irrigation and generate electricity
(d) To provide water for conservation of biological diversity

Natural Resources MCQ Class 10 Question 18.
Which of the following steps should be adopted in order to save the environment?
(a) Replace coal to firewood for cooking food
(b) Replace petroleum to coal in vehicles for transportation
(c) Replace thermal power with solar power to generate electricity
(d) Replace the use of coal to petroleum for melting metals in a furnace

### Assertion Reasoning questions Class 10 Science Chapter 16

For the following questions, two statements are given – one labeled Assertion (A) and other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

MCQ Questions On Sustainable Management Of Natural Resources Question 19.
Assertion (A): Sustainable development implies a change in all aspects of life.
Reason (R): Economic development is linked to environmental conservation.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.

(Competency Based Questions (CBQs))

Question 1.
Find out about the international norms to regulate the emission of carbon dioxide. Have a discussion in class about how we can contribute towards meeting those norms.
There are a number of organisations that seek to spread awareness about our environment and promote activities and attitudes that lead to the conservation of our environment and natural resources. Find out about the organizations) active in your neighbourhood/ village/town/city.
(A) Which of the following greenhouses gas is present in very large quantities?
(a) Ozone
(b) Methane
(c) Carbon dioxide
(d) Propane

(B) Select the incorrect statement from the statements given below:
(a) Increased emission of greenhouse gases is a natural process.
(b) Life on earth is possible due to presence of greenhouse gases.
(c) Greenhouse effect is a natural process that maintains earth’s temperature.
(d) More is the emission of greenhouse gases, more is the temperature of the earth’s atmosphere.
(a) Increased emission of greenhouse gases is a natural process.

Explanation: The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs) The absorbed energy warms the atmosphere and the surface of the Earth. This process maintains the Earth’s temperature at around 33 degrees Celsius warmer than it would otherwise be, allowing life on Earth to exist.

The problem we now face is that human activities – particularly burning fossil fuels (coal, oil and natural gas), agriculture and land clearing – are increasing the concentrations of greenhouse gases. This is the enhanced greenhouse effect, which is contributing to warming of the Earth.

(C) Which of the following are the causes of increased emission of carbon dioxide in India?
(I) Burning of coal for power generation
(II) Increased vegetation cover during monsoon.
(III) Burning of agricultural wastes
(IV) Burning of fossil fuels for transportation
(a) Only (I)
(b) Only (II)
(c) (I), (II) and (IV)
(d) (I), (III) and (IV)

(D) Which one of the following cannot be a goal or an international norm to regulate the emission of carbon dioxide:
(a) To limit and reduce greenhouse gases (GHG) emissions in accordance with agreed individual targets.
(b) To monitor actual emission of greenhouse gases.
(c) To invest in technological development in the developing countries.
(d) To assist countries in adapting to the adverse effects of climate change.
(c) To invest in technological development in the developing countries.

Explanation: The Kyoto Protocol is an international treaty which extends the 1992 United Nations Framework Convention on Climate Change (UNFCCC) that commits state parties to reduce greenhouse gas emissions, based on the scientific consensus that (part one) global warming is occurring and (part two) that human-made CO2 emissions are driving it. Although it has scope of assisting countries in adapting to the adverse effects of climate change, it does not have scope for investing in technological development in the developing countries.

(E) One of the ways individuals can contribute towards conservation of environment and natural resources is:
(a) Recycling, reusing, and composting
(b) Making better transport choices
(d) All of the above
(d) All of the above

Explanation: Individuals can contribute towards conservation of the environment and natural resources by reusing, recycling of waste materials, composting of organic wastes, making better transport choices and using public transport as much as possible and reducing electricity usage.

Question 2.
Make a list of forest produce that you use. What do you think a person living near a forest would use? What do you think a person living in a forest would use? Discuss with your classmates how these needs differ or do not differ and the reasons for the same. Find out about any two forest produce that are the basis for an industry. Discuss whether this industry is sustainable in the long run. Or do we need to control our consumption of these products?
(A) Which of the following are not products derived directly or indirectly from forest produce used by most urban people?
(a) Paper
(b) Natural gas
(c) Timber
(d) Dyes
(b) Natural gas
Explanation: Forests give us a lot of useful products such as paper, timber, dyes, medicines, fruits, spices, dyes and oils.

Natural gas on the other hand is a fossil fuel formed from the plants, animals, and microorganisms that lived millions of years ago.

(B) The table below lists the various stakeholders in forests. Select the row containing incorrect information:

 Stakeholders Justification (a) People who live in or around forests Dependent on forest produce for various aspects of their life (b) Forest Department of the Government Owns land and controls the resources from forest (c) Industrialists Dependent on forests In any one area as they use various forest produce (d) wild life and nature enthusiasts forests. Want to conserve nature in its pristine form

(C) Which of the following forest produce are used by the persons Living in a forest?
(I) Firewood and small. timber
(II) Bamboo
(III) Various agricuLtural. Implements made of Iron and steel.
(IV) Fruits, nuts and medicines
(a) Both (I) and (II)
(b) Both (II) and (IV)
(c) (II), (III) and (IV)
(d) (I), (II) and (IV)

(D) For which of the following needs are people Living near forests dependent on forests?
(a) Fodder fruit and agricultural implements
(b) Fuel, fodder and monoculture
(c) Fuel, fodder and cuLtivation
(d) Minerals, fodder and fuel

(E) We should conserve forests because:
(a) Forest provide us with oxygen and they cause rainfall.
(b) Forest prevents soil erosion.
(c) Various forest products are used as raw materials in industries.
(d) All of the above
(d) All of the above
Explanation: Conservation of forests is the need of the jour as forests provide us with oxygen, they prevent soil erosion, various industries are dependent upon forests for their raw materials and medicines.

Question 3.
Usually we put recycling on top of everything, but today on the 5 R process, it comes in last. Five actions should respectively be taken if possible before recycling any products. These R’s include: refuse, reduce, reuse, repurpose and finally, recycle. This is an important methodology for businesses to follow to ensure they can reduce waste and boost their recycling efforts. This ultimately lessens the amount of waste that will end up in landfill and will optimise your recycling programs.

(A) The main items that can be recycled are:
(II) Plastic (PET) bottles
(III) Egg cartons
(IV) Steel cans
Select the correct options from below:
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (1), (U) and (III)
(d) (I), (II) and (IV)
(d) (I), (II) and (IV)

Explanation: Among the items that can be recycled are lead acid batteries, plastic bottles, steel and aluminium cans, glass bottles, paper, cardboard boxes. Among the items that cannot be recycled are egg cartons, plastic shopping bags, drinking cups, plastic utensils and broken or sharp glass.

(B) The table below gives the meaning of the terms Reuse, reduce and reuse.
Select the row containing the correct meaning of the three terms

 Refuse Reduce Reuse (a) Use less of something Use something over and over again Make something into something new (b) Make something into something new Use less of something Use something over and over again (c) Say no to things that can harm environment Use less of something Use something over and over again. (d) Say no to things that can harm environment Use something over and over again. Use less of something

(C) How can organic waste be appropriately managed?
(a) Composting
(b) Recycling
(c) Burning
(d) Melting

(D) Look at the figure below and suggest which out of the five ‘R’s is represented below:

(a) Reuse, as plastic bottle is being used again.
(b) Repurpose, as the plastic bottle is being used for a different purpose.
(c) Reduce, as less of the thing is being used.
(d) Recycle, as plastic bottle is being recycled.

(E) The doorstep delivery of milk in glass bottles is an example of:
(a) Reduce
(b) Reuse
(c) Repurpose
(d) Recycle
(b) Reuse

Explanation: Reuse is the action or practice of using an item by taking, but not reprocessing, previously used items and it helps save time, money, energy and resources. In the doorstep delivery of milk in glass bottles, the delivery person gives a bottle containing fresh milk and the empty bottle is returned to him the next day. In this way, the glass bottles are reused.

Question 4.
Fossil fuels Like coal, oil, and natural gas present environmental problems starting with their extraction and going all the wag through to their use. They are all different in their properties and uses, but they have some similarities.We use fossil fuels for most of our energy needs today. Coal, natural gas, and oil accounted for 87 percent of global primary energy consumption. Burning coal for electricity is in decline, while the use of natural gas, solar and wind power are on the rise.

Complete combustion of coal and petroleum:
(I) increases air pollution
(II) increases effciency of machines.
(III) reduces global warming.
(IV) produce poisonous gases.
The correct option is:
(a) (I) and (II)
(b) (II) and (IV)
(c) (II) and (III)
(d) (III) and (IV)

Question 5.
Half of Delhi’s school-going population (some 2.2 million children) suffers from some or the other form of irreversible lung damage from poor air quality in the city. Research is now showing that pollution can weaken a child’s immune system and increase the risk of cancer, epilepsy, diabetes and even adult- onset diseases like multiple sclerosis. In adults, poor air quality causes one’s lung capacity to decrease, more headaches, sore throats, coughs, fatigue, even lung cancer.

In 2017, air pollution was the fifth-highest mortality risk factor globally – linked to 4.9 million deaths and 147 million years of healthy life otherwise lost. Reducing global air pollution to levels recommended by the WHO would increase life expectancy worldwide as much as eradicating breast and lung cancer would, according to a Quartz report from earlier this year. Going by National Health Profile of India 2015 report, there were 3.5 million reported cases of acute respiratory infection nationwide last year – a 1,40,000 increase on the previous year, and a 30 percent increase since 2010. The pie chart below shows the average levels of fine particulate matter having diameter less than 2.5 micrometers (PM2.5) in Delhi in the month of Nov 2020.

(A) According to the pie chart shown, the major contributors responsible for more than 80% of PM2.5 in air are:
(a) Road dust, Construction and demolition, hotels and restaurants, Industrial point sources
(b) Road dust, domestic sources, Diesel gensets, Industrial point sources
(c) Road dust, vehicles, Construction and demolition and Industrial point sources
(d) Road dust, vehicles, domestic sources and Industrial point sources

(B) The major air pollutants are:
(I) Nitrogen dioxide
(II) Sulphur
(III) Particulate matter
(IV) Ozone
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (III) and (IV)
(d) (I), (II) and (III)
(c) (I), (III) and (IV)

Explanation: The major air pollutants are: Ozone (O3), Nitrogen dioxide, Carbon Monoxide (CO), Sulphur Dioxide (SO2) and Particulate Matter (PM10 and PM2.5)

(C) Which of the following element is not present in coal and petroleum:
(a) Silicon
(b) Carbon
(c) Hydrogen
(d) Sulphur
(a) Silicon

Explanation: Coal and petroleum have been formed from biomass and contain carbon, hydrogen, nitrogen and sulphur.

(D) The number of years our known petroleum and coal reserves will last as per the present estimates is given in the table below.
Select the row containing the correct values:

 Number of years our known petroleum reserves will last Number of years our known coal reserves will last (a) 100 300 (b) 40 200 (c) 400 300 (d) 200 40

(b) Number of years our known petroleum reserve will last: 40; Number of years our known coal reserves will last: 200.

Explanation: As per the present estimates, the number of years our known petroleum and coaL reserves will Last are 40 years and 200 years respectively. This estimate is based on the present rate of usage of these fuels.

(E) Select the incorrect option:
The main reason for using coal and petroleum judiciously is:
(a) These lead to global warming
(b) These pollute our environment
(c) These are not limited
(d) These are not inexhaustible

Question 6.
When Sukanya visited her maternal grandparents during her school vacations, she observed that both her grandparents would switch off lights and fans when not in use. They would in fact encourage them also to use natural light as much as possible.

Switching off unnecessary lights and fans and repairing leaking taps correctly defines which term of 5R’s?
(a) Recycle
(b) Reuse
(c) Repurpose
(d) Reduce
(d) Reduce

Explanation: We can reduce the voltage of electricity by switching off unnecessary lights and We can reduce the voltage of water by repairing the leaking taps.

1. We can collect plastic, paper, glass and metal items and recycle these materials to make required things.
2. Reuse means to use the same things again eq. Plastic bottles of same or pickles can be used for storing things in the kitchen.
3. Repurpose: The object which can no more be used for the original purpose e.g. cups with broken handles can be used to grow small plants and as feeding vessels for birds.
4. Refuse to take the things people offer you that you don’t need or are harmful to the environment, e.g., take your own cloth or jute bag for shopping and refuse to accept plastic bag.

Question 7.
Poachers, traffickers and highly-organised criminal gangs decimate already endangered wildlife species, reaping a deadly harvest in the pursuit of profits. To address the problem, in 1973 the United Nations General Assembly signed the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), aimed at stemming the illegal trade in wild animals and rare commodities. UN World Wildlife Day is held each year on the anniversary of the signing. The day helps raise awareness of the many challenges facing the world’s wild animals and plants and the efforts to stamp out illegal trading.

(A) The main objective of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) is that it:
(I) Ensures that some species entering into international trade is threatened with extinction.
(II) Promotes the conservation and sustainable use of biodiversity
(III) Contributes to tangible benefits for poachers
(IV) Stops over exploitation of many endangered species
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (II) and (IV)

(B) Which of the following is a step taken by the government to protect the wildlife?
(a) Various Project to protect animals in forest
(b) Proper food facilities to the animals in forest
(c) Deforestation to provide space for urbanization
(d) Control the population of animals in forest
(a) Various Project to protect animals in forest

Explanation: The Government of India has taken various steps to conserve the wildlife. The major among them is establishing of various projects in order to protect the wildlife. Some of the projects are Project Tiger, Project Rhino, Project Great Indian Bustard and many more.

(C) Which of the following is the most important human activity Leading to the extinction of wildlife?
(a) Increased pollution of air, water and land
(b) Alteration and destruction of the natural habitats.
(c) Hunting of wild animals for valuable wildlife products
(d) Afforestation

(D) Which of the following will not be a result of uncovering half of the forest covering of the earth?
(a) Some wildlife species will become extinct
(b) Soil erosion will increase
(c) It will lead to climatic changes
(d) Forest dwelling people will be benefited.

(E) Which of the following is the name given to a scheme to protect and conserve bio-diversity?
(a) Biosphere
(b) Biotechnology
(c) Bio-reserve
(d) Bio-ecology
(c) Bio-reserve

Explanation: Bio-reserve is a scheme to protect and conserve bio-diversity. The central area preserves the flora and fauna. The surrounding zone is utilized for research and experiments regarding conservation of bio-diversity.

Question 8.
The first phase of the Ganga action plan was inaugurated by late Rajiv Gandhi at Rajendra prasad ghat of Banaras. The National Protection Agency was constituted for its implementation. During the first phase of Ganga Action Plan 256 schemes of 462 crores were undertaken in Uttar Pradesh, Bihar and West Bengal. Special stations have been created to check the quality of water. The experts from Bharat Heavy Electricals Limited and National Environment Engineering Research Institute were appointed to check the quality of the water.

The main purpose of the ‘Ganga Action Plan’ (GAP) project launched by the government in 1985 was to:
(a) Build new dams over the Ganga river
(b) Make its water pollution free
(c) Utilize the river water for irrigation purposes
(d) Promote the growth of water sports in the river

Question 9.
India’s water situation is dire. There are no two ways around it. Around 2,00,000 people die every year due to inadequate access to safe water, 21 major cities will run out of groundwater by 2020, 75% of households do not have access to drinking water at home and 70% of India’s water is contaminated. Plus the problem is only going to get more severe, as the population grows, while water becomes even more scarce. It should be evident, then that India is facing a water crisis, one that whoever comes to power would be expected to help resolve.

(A) The main causes of contamination of water are:
(I) Burning of fossil fuels
(II) Dissolved oxygen
(III) Untreated sewage
(IV) Agricultural runoff
(a) Both (I) and (II)
(b) Both (III) and (IV)
(c) (I), (II) and (IV)
(d) (I), (III) and (IV)
(d) (I), (III) and (IV)

Explanation: Canals, rivers and lakes in India often serve as dumping grounds for sewage, solid and liquid wastes. Water pollution is a major environmental issue in India. The largest source of water pollution in India is untreated sewage. Other sources is of pollution include agricultural runoff and unregulated small-scale industry. Burning of fossil fuels releases harmful gases like carbon dioxide, oxides of suLphur and nitrogen which cause acid rain and pollute the water bodies. Dissolved oxygen, when released in water, helps aquatic plants and animals for respiration. So it does not cause pollution, but the removal of dissolved oxygen causes pollution.

(B) Which of the following is not the main cause of water scarcity in India?
(a) Climate change
(b) River pollution
(c) Natural disasters
(d) Groundwater extraction and irrigation

(C) The main purpose of water harvesting is to:
(a) Use surface water for irrigation.
(b) Recharge ground water.
(c) Collect water directly for domestic use
(d) Refill lake water and other water bodies.

(D) The aims of Watershed management is:
(a) To increase the biomass production.
(b) To develop primary resources of land and water
(c) To produce secondary resources of plants and animals.
(d) All of the above
(d) All of the above

Explanation: Through watershed manage¬ment, one can implement plans, projects that sustain and enhance watershed functions. Watershed functions include capturing, storing and recharging groundwater, filtering out water pollutants, and secure release of rainwater to avoid floods during heavy rainfalls. Watershed management emphasises scientific soil and water conservation in order to increase the biomass production. The aim is to develop primary resources of land and water, to produce secondary resources of plants and animals for use in a manner which will not cause ecological imbalance.

(E) Some of the ancient water harvesting alongwith states where these were built are listed in the table below. Select the row containing incorrect information:

Explanation: Water harvesting is an age-old concept in India. Khadins, tanks and nadis in Rajasthan, bandharas and tals in Maharashtra, bundhis in Madhya Pradesh and Uttar Pradesh, ahars and pynes in Bihar, kulhs in Himachal Pradesh, ponds in the Kandi belt of Jammu region, and eris (tanks) in Tamil Nadu, surangams in Kerala, and kattas in Karnataka are some of the ancient water harvestings, including water conveyance, structures still in use today.

Question 10.
Groundwater, which can be used by people, constitutes only 0.8% of total water voLume while the rest Lies in the form of oceans and snow on mountains and glaciers. A growing population combined with huge demand of water for development purposes has put excessive stress on available water resources. The uneven distribution of water resources, artificial modification of natural flow of rivers and human abuse are the main reasons for the looming water crisis in India.The situation of groundwater is critical in Delhi, Punjab, Haryana and Rajasthan. These states need urgent attention from the government and the implementation of proper water management techniques to prevent severe water crises.

In addition to low rainfall, what are the other reasons for non-availability of water in arid and semi-arid zones of our country?
The reasons for the non-availability of water in arid and semi-arid zones of our country are:

1. No proper rain water harvesting systems in these areas.
2. Pollution of water due to mixing of industrial and domestic waste making it unfit for drinking purposes.

Question 11.
The Nagarjuna Sagar Dam is located in the state of Telangana. It is India’s largest Masonry Dams built till date. It is the largest manmade lake in the world. It has 26 gates and is 1.55 km in length. It is situated on the river Krishna.

Construction of a dam on a river often results in the reduction of fish catch. Why is it so?
Fish populations are highly dependent upon the characteristics of their aquatic habitat which supports all their biological functions. The water stored by constructing dams is stagnant water whereas fishes breed in clean and running water due to which their population decreases and fish catch also reduces.

Question 12.
Sanjay visited a National park with his parents to observe wild life. As they were entered the forest area, they observed logs of teak wood being transported from the forest in big trucks by a contractor.

Will the local people also behave in a similar manner? Justify your answer.
No, the local people will not behave in this manner. The reason is that the local people are dependent on the forest for their day to day sustenance since generations whereas for the contractor it is just a means of earning his livelihood. Once all the trees of a particular forest have been cut, the contractor will simply move on to a new forest.

Question 13.
You must be aware that the Indus valley civilization had been famous for its irrigation and water harvesting techniques and thus when it comes to Rain Water Harvesting, India has its pride. But why is it that despite having such an elaborate system and knowledge, the country is facing such extreme water shortage conditions? Bavaria are unique stepwells that were once a part of the ancient networks of water storage in the cities of Rajasthan. The irtle rain that the region received would be diverted to man-made tanks through canals built on the hilly outskirts of cities.The water would then percolate into the ground. raising the water table and recharging a deep and intricate network of aquifers. To minimise water loss through evaporation, a series of layered steps were built around the reservoirs to narrow and deepen the wells.

What are the advantages of water harvesting techniques?
Rainwater harvesting is the process of accumulating and storing rainwater for on-site use instead of allowing it to run off Rainwater provides an independent and free water supply that offers several ways the water can be used. It reduces soil erosion arid flooding, reduces demand an ground warer. makes water available for non-drinking purposes and helps in plant growth

Question 1.
Make a list of few industries that are dependent on forest products.
Forest product-dependent industries are: Timber, paper, lac and sports equipment industries.

Question 2.
Is Water conservation necessary? Give reason.
Water conservation is necessary as availability of water on Earth is more than enough for all but due to its uneven distribution, wide seasonal fluctuations in rainfall and majority of available water being saline, conservation is highly important for future generations.

Question 3.
How is the increase in demand for energy affecting atmosphere?
Overconsumption and increase in demand of fossil fuels releases a huge amount of polluting gases into the atmosphere, which in turn causes global warming and also produces acid rain.

## Our Environment Class 10 MCQs Questions with Answers

Our Environment Class 10 MCQ Question 1.
In the given food chain, suppose the amount of energy at the fourth trophic level is 5 kJ, what will be the energy available at the producer level?
Grass Grasshopper → Frog → Snake → Hawk
(a) 5 kJ
(b) 50 kJ
(c) 500 kJ
(d) 5000 kJ

Class 10 Science Chapter 15 MCQ Question 2.
The Foodweb is constituted by:
(a) relationship between the organisms and the environment
(b) relationship between plants and animals
(c) various interlinked food chains in an ecosystem
(d) relationship between animals and the environment

Our Environment Class 10 MCQ With Answers Question 3.
In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of:
(a) heat energy
(b) light energy
(c) chemical energy
(d) mechanical energy

Our Environment MCQ Class 10 Question 4.
Choose the incorrect statement from the following:
(a) Ozone is a molecule formed by three atoms of oxygen.
(b) Ozone shields the surface of the Earth from ultraviolet radiations.
(d) Ozone gets decomposed by UV radiations

Ch 15 Science Class 10 MCQ Question 5.
Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level constitute the:
(a) food web
(b) ecological pyramid
(c) ecosystem
(d) food chain
(a) food web

Explanation: Organisms of a higher trophic level feeding on several types of organisms belonging to a lower trophic level constitute the food web.

MCQ On Our Environment Class 10 Question 6.
Expand the abbreviation GAP:
(a) Governmental Agency for Pollution Control
(b) Gross Assimilation by Photosynthesis
(c) Ganga Action Plan
(d) Governmental Agency for Animal Protection
(c) Ganga Action Plan

Explanation: GAP, 1985 came in existence to check water pollution in river Ganga.

Class 10 Our Environment MCQ Question 7.
Which of the following are biodegradable substances?
(a) Glass bottle, Grass
(b) Jutebag, polythene bag
(c) Cotton cloth, vegetable peels
(d) DDT, Pen refill

MCQ Of Our Environment Class 10 Question 8.
Which of the statement is incorrect?
(a) Producers form the first prophic level.
(b) Produces trap solor energy and transform it into chemical energy in food.
(c) All plants are producers.
(d) Nutrients and energy enter the living world through producers.

Class 10 Science Ch 15 MCQ Question 9.
Which of the following limits the number of trophic levels in a food chain?
(a) Decrease in energy at higher trophic levels
(b) Deficient food supply
(c) Polluted air
(d) Water

Chapter 15 Class 10 Science MCQ Question 10.
In the given figure, the various trophic levels are shown in a pyramid. At which trophic level is maximum energy available?

(a) T4
(b) T2
(c) Ti
(d) T3

Chapter 15 Science Class 10 MCQ Question 11.
Disposable plastic plates should not be used because:
(a) they are made of materials with light weight
(b) they are made of toxic materials

Environment Class 10 MCQ Question 12.
Which one of the following stakeholders of forests causes the maximum damage to forest?
(a) People who live in or around the forest
(b) The forest department of the government
(c) The wildlife and native enthusiasts
(d) The industrialists
(d) The industralists

Class 10 Chapter 15 MCQ Science Question 13.
Food web is constituted by:
(a) Relationship between the biotic and abiotic components of ecosystem.
(b) Relationship between abiotic compo-nents and recycling of nutrients.
(c) Relationship between biotic compo-nents and biogeochemical cycles.
(d) Various interlinked food chains in an ecosystem.

Class 10 Science Chapter 15 MCQ Online Test Question 14.
Consider a terrestrial food chain: Grass Grasshopper → Frog → Snake → Eagle
The energy transfer in the above food chain will be from:
(I) Producer to decomposer
(II) Producer to primary consumer
(III) Primary consumer to secondary consumer
(IV) Tertiary consumer to Secondary consumer
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (III) and (IV)

MCQ Of Chapter 15 Science Class 10 Question 15.
Which of the statements regarding food chain are correct?
(I) All food chains are of equal length and complexity.
(II) Food chains generally consist of only three or four steps.
(III) The greatest number of organisms in a food chain is of the producers.
(IV) Relationships between organisms can be shown only by straight lines.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) (II), (III) and (IV)

Question 16.
Ozone-depleting substances are chiefly utilized in
(I) chimneys
(II) cooling and refrigeration applications and in the manufacturer of foam products
(III) all of the human activities
(IV) burning fossil fuels
(a) Only (I)
(b) Only (II)
(c) (I), (II) and (IV)
(d) (II), (III) and (IV)

Question 17.
Consider the chemical reactions taking place at upper atmosphere:

Select the row containing the correct naming of A, B and C.

(a) A: Molecular oxygen; B: Ultraviolet radiations; C: Ozone molecule

Explanation: Ozone at the higher levels of the atmosphere is a product of Ultraviolet radiation acting on oxygen (02) molecule. The higher energy UV radiations split apart some molecular oxygen (O2) into free oxygen (O) atoms and these atoms then combine with the molecular oxygen to form ozone as shown below:

Question 18.
The food habits of the organisms at the second and fourth trophic levels of a typical terrestrial are given in the table below.
Select the row containing the correct food habits:

Question 19.
The protocol agreed upon in 1987 organized by the United Nations Environment Programme (UNEP) is related to:
(a) Food security
(b) Ozone layer depletion
(c) Global warming
(d) Sustainable deveLopment
(b) Ozone Layer depletion

Explanation: In 1987. the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 Levels in order to stop the depletion of ozone layer.

Question 20.
(c) Atmospheric oxygen
(d) CFC

Question 21.
Which organism shown in the food chain above wouLd Contain the greatest concentration of chemical pollutants?
Phytoplankton → Krill → Small fish → Tuna → Shark
(a) Phytoplankton
(b) KriLl
(c) Tuna
(d) Shark

### Assertion Reasoning questions Class 10 Science Chapter 15

For the following questions, two statements are given one labeled Assertion (A) and the other Labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given beLow:
(a) Both (A) and (R) true and (R) is correct explanation of the assertion
(b) Both (A) and (R) are true and (R) is correct Explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 22.
Assertion (A): Green plants of the ecosystem are the transducers.
Reason (R): Producers trap the radiant
energy of the sun and change it into chemical energy.
(a) Both (A) and (R) are true and (R) is the correct explanation of assertion. Explanation: Green plants can make their own food. Hence, they are called producers. Since they capture the heat of the Sun to prepare their food, they are also called transducers. The plants prepare their food by trapping the energy of the Sun. They convert this light energy to chemical energy to form ATP molecules.

Question 23.
Assertion (A): Food chains generally consist of only three to four steps.
Reason (R): Autotrophs capture solar energy and convert it into chemical energy.

Question 24.
Assertion (A): The maximum concentration of chemicals and pesticides occurs at the first trophic leveL
Reason (R): The chemicals and pesticides are not biodegradable.

Question 25.
Assertion (A): Ozone shields the surface of the earth from ultraviolet radiation from the sun.
Reason (R): Ozone at the higher levels of the atmosphere is a product of UV radiations acting on oxygen molecules.
(a) Both (A) and (R) are true and (R) is the correct explanation of assertion. Explanation: Ozone is formed when the high-energy UV radiations act on oxygen molecules (O2) and split it into free oxygen atoms (O) which combine with the molecular oxygen to form ozone (O3). Ozone thus shields the earth’s surface from the harmful effects of UV radiation.

Question 26.
Assertion (A): Improvements in our lifestyle have resulted in lesser amounts of waste material generation.
Reason (R): Changes in packaging have resulted in much of the waste generated being non-biodegradable.
(d) (A) is false, but R is true.

Explanation: Improvements in our lifestyle have resulted in greater amounts of waste material generation due to changes in attitude and more and more things we use becoming disposable, which are also non-biodegradable.

Question 27.
Assertion (A): Frogs mostly occupy the second trophic level in food chains.
Reason: Frogs mostly feed on insects that depend on plants.
(d) A is false, but R is true.

Explanation: Frogs mostly occupy the third trophic level in the food chain since they feed on insects which depend on plants and plants are the primary producers thus they occupy the first trophic level in the food chain. Thus A is false, but R is true.

Question 28.
Assertion(A): In the food chain third trophic level is occupied by Carnivores.
Reason(R): Some of the carnivores are secondary consumers.

Question 29.
Assertion (A): Each step of the level of the food chain forms a trophic level.
Reason (R): The organisms occupying the first trophic levels are called autotrophs.
(a) Both (A) and (R) are true, and (R) is the correct explanation of the assertion.

Question 30.
Assertion (A): Each step or level of the food chain forms a trophic leveL
Reason (R): The various components of the ecosystem are interdependent.

Question 31.
Assertion (A): Polythene bags are non-biodegradable substances.
Reason (B): These bags cannot be broken down by microorganisms to simpler substances.

Question 32.
Assertion (A): The food chains generally consist of only three or four steps.
Reason (B): Our food grains such as wheat and rice, vegetables and fruits and even meat contain varying amounts of pesticides.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.

Explanation: The food chains generally consist of only three or four steps because after that the energy added to the biomass of each level is reduced and at the fourth trophic level it will be least. Thus Both A and R are true, but R is not the correct explanation of the assertion

Question 33.
Assertion (A): The amount of ozone in the atmosphere began to increase sharply in the 1980c.
Reason (R): The United Nations environment program (UNEP) succeeded in forging an agreement to freeze CFC production in 1987.
(d) A is false, but R is true.

Explanation: The amount of ozone in the atmosphere began to decrease sharply in the 1980s because of the United Nations environment program (UNEP) succeeded in forging an agreement to freeze CFC production in 1987. Thus A is false, but R is true.

(Competency Based Questions (CBQs))

Question 1.
India today is facing the problem of overuse of resources, contamination of water and soil and lack of methods of processing the waste. The time has come for the world to say goodbye to “single-use plastics.” Steps must be undertaken to develop environment-friendly substitutes, effective plastic waste collection and methods of its disposal.

Indore treated 15 lakh metric tonnes of waste in just 3 years, through biomining and bioremediation techniques. Bioremediation involves introducing microbes into a landfill to naturally ‘break’ it down and biomining involves using trommel machines to sift through the waste to separate the ‘soil’ and the waste component.

The city managed to chip away 15 lakh metric tonnes of waste at a cost of around? 10 crore. A similar experiment was successfully carried out in Ahmedabad also.
(A) State two methods of effective plastic waste collection in your school.

(B) Name any two uses of “single-use plastic” in daily Life.
Uses of “Single-use plastic” in daily life.

1. In medical field: Plastic syringes, plastic gloves are made of single-use plastic and are used so that infection can be controlled.
2. Single-use plastic is also used in food industry for packing, straws, wrappers, spoons etc.
3. In emergency/ disaster situations where food and water has to be transported. Plastic will be light in weight and this packaging will be helpful to transport.

(C) If we discontinue the use of plastic, how can an environment-friendly substitute be provided?

(D) Do you think microbes will work similarly in landfill sites as they work in the laboratory? Justify your answer.
No, the microbes will not work similarly in landfill sites as they work in laboratory. Microbes need suitable conditions like temperature, moisture etc. and nutrients to grow. In laboratory we provide this atmosphere artificially to microbes for their growth but landfill sites do not have suitable atmosphere to grow.

Question 2.
Prerna visited a farm along with her family. Her younger brother was interested in knowing what kind of food is eaten by animals such as cows, buffaloes and deers. She told her brother that all these animals are herbivores as these eat only grass and plants.

How much of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores?
(a) 100%
(b) 10%
(c) 1%
(d) 0.1%
(b) 10%

Explanation: 10% of the net primary productivity of terrestrial ecosystem is eaten and digested by herbivores. According to 10% law, only 10% of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.

Question 3.
Human body is made up of five important components, of which water is the main component. Food, as well as potable water, are essential for every human being. The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields.

These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants. As these chemicals are not biodegradable, they get accumulated progressively at each trophic level.

The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body.
(A) Why is the maximum concentration of pesticides found in human beings?
As human beings occupy the top level in any food chain, the maximum concentration of these chemicals get accumulated in our bodies due to biological magnification.

Explanation: Pesticides are being used extensively for a high yield in the fields. These pesticides mix up with soil and water. From soil and water, these pesticides are absorbed by the plants along with water and minerals. When herbivores eat this plant food, these chemicals pesticides go into their bodies through the food chain. When the next trophic level, carnivores eat herbivores, these pesticides get transferred to their bodies. As these chemicals are not biodegradable, they get accumulated progressively at each trophic level.

(B) Give on method which could be applied to reduce our intake of pesticides through food to some extent.

• We can reduce our intake of pesticides through food to some extent:
• Wash fruits and vegetables before eating. Buy organic and locally grown fruits and vegetables.
• Use non-toxic methods for controlling insects in the kitchen garden. (Anyone).

(C) Various steps in a food chain represent:
(a) Food web
(b) Trophic level
(c) Ecosystem
(d) Biomagnification

(D) With regard to various food chains operating in an ecosystem, man is a:
(a) Consumer
(b) Producer
(c) Producer and consumer
(d) Producer and decomposer

Question 4.
Driving the Swach Bharat Abhiyaan forward, several NCOs are working towards the instaLLation of Blue and Green Dustbins for Municipal Corporations and schools in New Delhi. They are also carrying out a drive to educate children about the segregation of two different kinds of waste. The green is meant for wet waste and the blue one is for dry waste. This way they are separating biodegradable waste from non-biodegradable, thus providing various recycling and composting benefits and keeping the neighborhood clean and healthy.

In the following groups of materials, which group(s) contain(s) only non-biodegradable items?
(I) Wood, paper, leather
(II) Polythene, detergent, PVC
(III) Plastic, detergent, grass
(IV) Plastic, Bakelite, DDT
(a) (I)
(b) (II)
(c) (I) and (II)
(d) (II) and (IV)

Question 5.
Series of organisms taking part at various biotic levels form a food chain. Each step or level of the food chain forms a trophic level. The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for heterotrophs or the consumers.
The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the third and larger carnivores or the tertiary consumers form the fourth trophic level.
The interactions among various components of the environment involve flow of energy from one component of the system to another.
(A) What are trophic levels?
Decomposers are microorganisms which breakdown complex organic substances into simple inorganic substances and help in recycling of nutrients. They feed on the dead and decaying bodies of plants and animals. They return the nutrients back to the soil and thus help in making this ecosystem stable e.g. fungi, bacteria.

(B) Give an example of a food chain.

(C) What is the role of decomposers in the ecosystem?

(D) Explain why the number of trophic levels in a food chain is limited?
Only 10% of the energy gets transferred from one trophic level to the next. So after 3 or 4 trophic levels, the energy available for passing on is too less to support another trophic level. Very little usable energy remains after 4 trophic levels. Hence the number of trophic levels in a food chain is limited.

Question 6.
Nitya observed her grandmother making compost which she used to give to her plants. Composting is the natural process of recycling organic matter, such as leaves and food scraps, into a valuable fertilizer that can enrich soil and plants. Anything that grows decomposes eventually; composting simply speeds up the process by providing an ideal environment for bacteria, fungi, and other decomposing organisms (such as worms, sowbugs, and nematodes) to do their work. The resulting decomposed matter, which often ends up looking like fertile garden soil, is called compost. Fondly referred to by farmers as “black gold,” compost is rich in nutrients and can be used for gardening, horticulture, and agriculture.

The decomposers in an ecosystem:
(a) convert inorganic material to simpler forms
(b) convert organic material to inorganic forms
(c) convert inorganic material to organic compounds
(d) do not breakdown organic compounds
(b) convert organic material to inorganic forms Explanation: The microorganisms, comprising bacteria and fungi, break down the dead remains and waste products of organisms. These microorganisms are the decomposers as they break down complex organic substances into simple inorganic substances that go into the soil and are once more used up by the plants.

Question 7.
You might have seen an aquarium, in the first activity, let us try to design an aquarium. What are the things that we need to keep in mind when we create an aquarium? The fish would need a free space for swimming (it could be a large jar), water, oxygen and food. We can provide oxygen through an oxygen pump (aerator) and fish food which is available in the market. If we add a few aquatic plants and animals it can become a self sustaining system.
In the second activity, while creating an aquarium did you take care not to put an aquatic animal which would eat others? Write the aquatic organisms in order of who eats whom and form a chain of at least three steps. A → B → C
(A) Identify the human-made ecosystems from the following:
(I) Ponds
(II) Crop fields
(III) Aquarium
(IV) Lakes
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (III) and (IV)
(d) (II), (III) and (IV)
(b) Both (II) and (III)

Explanation: Ponds and lakes are natural ecosystems, although there are some artificial or human made Lakes too. Aquariums and crop fields are human made ecosystems as these have been made by humans.

(B) The biotic and abiotic components in an aquarium are listed in the table below. Select the row containing the correct answer:

 Biotic Components Abiotic Components (a) Aquatic plants and animals, water Glass tank, aerator (b) Glass tank, aquatic plants and animals Water, aerator (c) Aquatic plants and animals Glass tank, water, aerator (d) Glass tank, water, aerator Aquatic plants and animals

(a) Ponds are natural ecosystems whereas aquariums are artificial ecosystems.
(b) There are less fishes in an aquarium as compared to a pond or lake
(c) The size of fishes is small in an aquarium as compared to a pond or lake
(d) Decomposers are absent in an aquarium whereas they are present in ponds or lakes.

(D) What would have happened if we had put predator fishes in the aquarium?
(a) They would eat all the smaller fishes thereby generating lot of waste.
(b) They would eat away all the food available in the aquarium.
(c) They would compete with smaller fish for food and nutrition.
(d) They would not pose any problem in the aquarium.

(E) Consider the following aquatic food chain consisting of three steps:

Identify the organisms at A, B and C:
(a) A: Zooplankton; B: Phytoplankton; C: Large fish
(b) A: Phytoplankton; B: Zooplankton; C: Small fish
(c) A: Zooplankton; B: Phytoplankton; C: Small fish
(d) A: Phytoplankton; B: Zooplankton; C: Large fish

Question 8.
Ritu went to the shopping mall to buy some gifts for her parents on their wedding anniversary. She was pleasantly surprised to see that all shop owners were giving the items purchased in beautiful and coloured paper bags instead of plastic bags.

Why is it better to use paper bags than plastic bags?
Paper is a biodegradable material, as it is obtained from wood whereas plastic is a non- biodegradable material. Therefore, paper is environment friendly whereas plastic causes environmental pollution.

Question 9.
In the first activity, find out what happens to the waste generated at home. Find out how the local body (panchayat, municipal corporation, resident welfare association) deals with the waste. Are there mechanisms in place to treat the biodegradable and nonbiodegradable wastes separately?
Calculate how much waste is generated at home in a day. How much of this waste is biodegradable? Suggest ways of dealing with this waste.
Next, find out how the sewage in your locality is treated. Are there mechanisms in place to ensure that local water bodies are not polluted by untreated sewage. Find out how the local industries in your locality treat their wastes.
(A) In the following groups of waste generated at home, which group contains only biodegradable items?
(a) Glass bottles, news paper, used tea leaves
(b) Polythene, detergent, Plastic packets
(c) Vegetable peels, paper, flowers
(d) Plastic packets, PVC, Glass bottles
(c) Vegetable peels, paper, flowers

Explanation: Biodegradable substances are those substances which are easily degraded by natural processes by the action of microorganisms. All materials of plant and animal origin are biodegradable whereas man made substances such as plastic, detergents, PVC, glass, etc are non- biodegradable.

(B) Based on the study of how most local municipal authorities deal with the wastes generated at home, following statements are written. Select the incorrect statement.
(a) The waste generated at home are differentiated into biodegradable and non-biodegradable materials.
(b) All types of wastes are placed in a single bin.
(c) Most of the “dry-waste” is processed at waste-to-energy plants.
(d) Most of the “wet-waste” is sent for composting

(C) Which of the following is not the correct practice of dealing with biodegradable wastes?
(a) Composting
(b) Anaerobic digestion of waste
(c) Landfills
(d) Burning

(D) Select the correct statements regarding treatment of sewage in any locality:
(I) Sewage is treated at sewage treatment plants.
(II) Sewage treatment is the process of removing contaminants from industrial wastewater only.
(III) Physical, chemical, and biological processes are used to remove contaminants and produce treated wastewater.
(IV) Sewage is treatment is the process of removing contaminants from domestic and municipal wastewater.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (I) and (IV)

(E) The best practice followed by local industries in treating their wastes is:
(a) Source reduction and reuse
(b) Incineration
(c) Dumping solid wastes in open drain
(d) Dumping chemical wastes directly into water bodies

Question 10.
Vijay’s science teacher was once sharing experiences about his village life. He explained how as a child, he would often hear the sound of frogs during nights and especially during the rainy days. But the situation has changed now with lesser population of frogs even in villages.

The number of malaria patients in a village increased tremendously when large number of frogs were exported from the village? What could be its cause?.

Question 11.
The sun is the ultimate source of light and heat for planet Earth and sets in motion very large and complex systems that develop and sustain life. One such land-based ecosystem is the forest, supporting a biodiverse set of plants, which in turn provide food for other living things. Several distinct types of woodland habitats exist on Earth, such as conifer, deciduous and mixed. A study of the deciduous forest shows how a food chain functions within an ecosystem that experiences distinct seasonal changes.

(A) In an ecosystem, the main source of energy is
(a) heat released during transpiration
(b) solar energy
(c) heat released during respiration
(d) water
(b) Solar energy

Explanation: Sun is the main source of energy for an ecosystem since green plants or producers are able to synthesize food only with the help of solar energy .

(B) Refer to the figure of food chain given above, identify A, B, C and D and select the correct combination of plots provided in the table below.

(d) A: Producer; B: Primary Consumer; C: Secondary Consumer; D: Tertiary Consumer

Explanation: In all food chains, the green plants are the producers as they synthesize food by utilizing solar energy. The small insects marked !B’ or herbivores are the primary consumers as they feed on plants. Small animals marked ‘C’ are secondary consumers as they feed on small insects and similarly larger carnivores are tertiary consumers and marked ‘D‘ and ‘E’.

(C) Which of the following are functional components of an ecosystem?
(I) Decomposers
(II) Solar energy
(III) Energy flow
(IV)Air
(a) Both (I) and (II)
(b) Both (III) and (IV)
(C) (I), (II) and (IV)
(d) (I), (III) and (IV)

(D) The correct identification of P and Q from the figure of food chain given is:
(a) P: Decomposers, Q: Nutrients
(b) P: Decomposers, Q: SoiL
(c) P: Producers, Q: Nutrients
(d) P Tertiary Consumers, Q: SoiL

(E) The effect of completely removing ‘P’ from the food chain would be:
(a) Energy flow would be blocked
(b) Movement of minerals back to soil will be blocked
(c) Rate of decomposition would increase
(d) No carbon dioxide will be available for herbivores for respiration
(b) Movement of minerals back to soil will be blocked

Explanation: The organisms marked ‘P’ are the decomposers which help in cleansing our environment by feeding on dead and decaying organisms. They help in movement of minerals or nutrients back to the soil for the producers.

Question 12.
Sanket and his friends went to a nearby orchard to see how different fruits are cultivated. However, they observed that pesticides were being sprayed on the fruits without adhering to any guidelines.

How can excessive use of pesticides to protect the crops from diseases cause long-term damage to mankind?
Pesticides are non-biodegradabLe chemicals which enter our food chain through the fruits we eat or are absorbed by the aquatic plants and animals. These concentration of these chemicals increases progressively at each trophic level and maximum concentration is found in human beings. This is known as biological magnification.

Question 13.
Ozone (O3) is a gas which is present naturally within Earth’s atmosphere and is formed of three oxygen atoms. In the figure we see a standard profile of ozone gas concentration through the Earth’s atmosphere, extending from ground level up to 40 kilometres in altitude. Ozone plays a different role in atmospheric chemistry at different heights in the Earth’s atmosphere. We can differentiate this profile into two key zones:

Tropospheric ozone is that which is present in the lower atmosphere. Throughout most of the troposphere, ozone concentrations are relatively low (as shown in the diagram). Ground-level ozone can have negative impacts on human health and is therefore commonly referred to as ‘bad’ ozone.

Stratospheric ozone is that which is present in the upper atmosphere. As shown in the diagram, concentrations of ozone are higher in the stratosphere than in the troposphere.

The stratosphere includes the zone termed the ‘ozone layer’. In the ozone layer, it is often referred to as ‘good’ ozone since it plays a crucial role in absorbing potentially dangerous ultraviolet (UV-B) radiation from the sun.

(A) Study the above graph and select the row containing the correct information:

 Good Ozone Bad Ozone Ionosphere Mesosphere Stratosphere Ionosphere Stratosphere Troposphere Mesosphere Troposphere

(c) Good ozone: Stratosphere; Bad ozone: Troposphere

(B) Ozone at higher atmosphere is a product of:
(a) Ultraviolet radiation acting on free oxygen.
(b) Infrared radiation acting on oxygen molecule.
(c) Infrared radiation acting on free oxygen.
(d) Ultraviolet radiation acting on oxygen molecule.

(C) Select the incorrect statements regarding ozone gas:
(I) It is present only in troposphere.
(II) It is present in very small quantities in stratosphere.
(III) It can be beneficial or harmful, depending upon its location and concentration.
(IV) It shields the surface of the earth from ultraviolet (UV) radiation from the Sun.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (II) and (111)
(d) (II), (III) and (IV)
(a) Both (I) and (II)

Explanation: Ozone is present in very low concentration in the lower atmosphere or troposphere, it is present in higher concentrations in the upper atmosphere or stratosphere. It is quite harmful when present in the lower atmosphere as it causes several diseases in humans. It is beneficial when present in upper atmosphere as it shields the surface of the earth from the harmful ultraviolet radiations of the sun.

(D) Which of the following products contain ozone-depleting substances?
(a) Motorbike, car with AC, Pesticides, Fire extinguisher
(b) Car with AC, refrigerator, fire extinguisher, aerosol sprays
(c) Motorbike, aerosol sprays, Pesticides, Fire extinguisher
(d) Heater, car with AC, Pesticides, Fire extinguisher

(E) Which of the following is not the consequence of ozone layer depletion?
(a) Increased ultraviolet rays
(b) Malignant melanoma-Another form of skin cancer
(c) Cataracts and other eye damage
(d) Tides

Question 14.
Monty was travelling to Delhi by road from Chandigarh. He observed a huge mountain like structure on GT Karnal road upon entering Delhi. He came to know that it was actually a landfill site and that Delhi has three landfill sites, viz. at Okhla, Bhalswa and Ghazipur. One can find waste burning at any give time in these landfills. They have also run out of space nearly a decade ago. Although the permissible limit for a garbage dumping is set to 20 meters, these sites have turned into huge mountains well beyond the permissible limit.

Suggest two measures to manage the garbage we produce.
Two measures to manage the garbage we produce are listed below:
(1) Segregate the wastes and try to reuse as many items as possible.
(2) Put wet and dry wastes in separate garbage bins so that they can be easily recycled.

Question 15.
Toxic substances move up the food chain and become more concentrated at each level. These substances are often pollutants from industries or pesticides from farming. Consider any small fish that eats plankton that has been tainted with mercury. Hundreds of small fish might then contain just few parts of the mercury, not enough to cause major harm. A bird then might eat hundreds of the small fish. so that now instead of 200 ppm ¡n a single fish, that bird has much higher Levels of mercury. The toxin amplifies as it moves up the food chain. The amount of mercury is measured in ppm, which means parts per million.

(A) The phenomenon when concentrations of a harmful substance increases in organisms at higher trophic LeveLs in a food chain or food web is:
(a) Artificial eutrofication
(b) Biological accumulation
(c) Biological magnification
(d) Biological pollution

(B) The table below gives the organism in a food web containing the Lowest and highest concentration of harmful chemical pollutants.
Select the row containing the correct answer.

 Lowest Concentration Highest Concentration (a) Primary consumers Secondary consumers (b) Tertiary consumers Producers (c) Producers consumers Secondary (d) Producers consumers Tertiary

(d) Lowest Concentration: Producers Highest Concentration: Tertiary consumers

Explanation: The concentration of harmful chemical pollutants such as DDT and other pesticides increases progressively at each trophic level Therefore, tertiary consumers which occupy the highest trophic level will have the highest concentration and producers which occupy the Lowest trophic level will have the lowest concentration of harmful chemical pollutants.

(C) Which of the following statements are incorrect?
(I) Non-biodegradable wastes are biological in origin.
(II) Biodegradable wastes are degraded by microorganisms such as bacteria and fungi.
(III) Biodegradabte wastes enter the food chain and get biologically magnified.
(IV)Non-biodegradable wastes are absorbed by plants from the soil.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) Both (III) and (IV)
(b) Both (I) and (III)

Explanation: The biodegradable wastes are biological in origin whereas non-biodegradable wastes are plastic, metals etc. The non-biodegradable wastes enter the food chain and get biologically magnified as we higher up the food chain.

(D) It was observed that at places where DDT was used to control mosquitoes and other pests, the eggs of eagles would become fragiLe and break and the eagle almost became extinct. After DDT was banned by Lawmakers, eagle population has recovered.
The possible reason for this is:
(a) DDT is non-biodegradable and hence found in Largest concentration in tertiary consumers.
(b) DDT is non-biodegradable and found in Largest concentration in producers.
(c) Largest concentration of DDT is found in secondary consumers on which eagle feeds.
(d) DDT is a strong chemical which makes the eggs fragile.

(E) Biological magnification is a result of
(a) climate change
(b) food shortages
(c) pollution
(d) extinction

Question 16.
The chemical energy of food is the main source of energy required by all living organisms. This energy is transmitted to different trophic levels along the food chain. The energy flow in the ecosystem is one of the major factors that support the survival of such a great number of organisms. For almost all organisms on earth, the primary source of energy is solar energy.

(A) The flow of energy in an ecosystem is:
(a) Omnidirectional
(b) Unidirectional
(c) Bidirectional
(d) May be unidirectional or bidirectional

(B) Non-biodegradable wastes enter the food chain through:
(I) Soil
(II) Water
(III) Air
(IV) Decomposers
(a) Both (I) and (II)
(b) Both (II) and (IV)
(c) Both (I) and (III)
(d) Both (III) and (IV)
(a) Both (I) and (II)

Explanation: The non-biodegradable pesticides are either washed down into the soil or into the water bodies. From the soil, these are absorbed by the plants along with water and minerals, and from the water bodies these are taken up by aquatic plants and animals and hence enter the food chain.

(C) What happens to the solar energy incident on the autotrophs in a terrestrial ecosystem?
(a) It is completely captured and converted into food energy by the autotrophs.
(b) A part of it is reverted to the solar input
(c) A part of it is captured and passes to the herbivores.
(d) It moves progressively through the various trophic levels in both directions.

(D) In the given food chain, suppose the amount of energy at fourth trophic level is 8 kJ.
Grass → Grasshopper → Frog → Snake → Hawk
Select the row containing the correct values of the energy available at the producer level and secondary consumer level?

 Energy Available Producer Level Energy Available at Secondary Consumer Level (a) 800kJ 8kJ (b) 800kJ 80kJ (c) 8000kJ 72kJ (d) 8000kJ 80kJ

(E) If only 10% of the energy from one trophic level passes up to the next level, what happens to the 90% energy that is not passed on?
(a) It is lost as heat to the environment
(b) It is used in digestion of food and in doing work.
(c) It is used for growth and reproduction.
(d) All of the above
(d) Energy Available at Producer Level: 8000 Id; Energy Available at secondary consumer level: 80 kJ

Explanation: According to 10 percent law, 90% of the energy captured from the previous trophic level is lost to the environment and only 10 percent is made available to the next trophic level.
in this food chain, at the 4th trophic level, 8 kJ energy is available to the snake. Therefore, we can calculate backwards to find energy available at the third, second and first trophic levels.

• Energy available to Snake (Tertiary consumer) = 8 kJ = 10% of 80 kJ
• Energy available to Frog (Secondary consumer) = 80 kJ = 10% of 800 kJ
• Energy available to Grasshopper (Primary consumer) = 800 kJ = 10% of 8000 kJ.
• The energy available to Grass (Producer) = 8000 kJ

Question 1.
List two main components of an ecosystem.
Two main components of an ecosystem are

1. Biotic component
2. Abiotic component

Question 2.
What is meant by ‘biological magnification’?
Biological magnification is the process by which the harmful and toxic substances enter the food chain and get concentrated in the body of living organisms at each successive level in food chain.

Question 3.
Examples of man-made ecosystems are aquarium, crop-fields, zoo, botanical garden, Greenhouse

Related Theory
An ecosystem is a self-sustained unit that comprises of all the interacting living things together with their non-living environment Manmade or artificial ecosystems that are carefully maintained in controlled environment.

Biodiversity in the man-made ecosystem will be very low as compared to natural ecosystem.

Question 4.

Question 5.
What is meant by tropic level in a food chain? Construct a terrestrial food chain with four trophic levels. The energy flow in a food chain is always unidirectional. Why?
Trophic level = Each step or level of the food chain forms a trophic level.

1. The ultimate source of energy used by living organisms is the sun.
2. Only 1% of solar radiations are captured by green plants in a terrestrial ecosystem and converted into food energy by photosynthesis. This energy is stored as chemical energy of food.
3. When green plants (producers) are eaten by primary consumers (Herbivores) a lot of heat is lost as heat to the environment and other activities. Only 10% of the food eaten is turned into its new body and is available for the next level of consumers (Primary carnivores).
4. Only 10% amount of organic matter reaches the next level of consumers (secondary carnivores).
5. Since, amount of available energy goes on decreasing at each trophic level, food chains usually consist of only 3 to 4 trophic levels. For example, grass receives 6000 J of energy from the sun. It will pass 10% of energy as per 10% law to grasshopper i.e. 600 J and so on.

Question 6.
What will be the amount of energy available to the organisms of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules?

Question 7.
Why do producers always occupy the first trophic level on every food chain?

Question 8.
Give 2 examples of each:
(A) Organisms occupying the first trophic level
Organisms occupying the first trophic level: trees, shrubs, grass.

Related Theory
Green plants make their own food by the process of photosynthesse. The food or energy is transferred from one organism to the other through food chain. So the srarting point of a food chain in produces i.e., plant occupy the first prophic level.

(B) Abiotic factors of an ecosystem
Abiotic factors of an ecosystem: soil, water, Light.

Related Theory
All the ecolytems are made of the main components biotic and abiotic components. The biotic component (living organisms) interact continuously with abiotic component (non-living component).

Question 9.
What are the advantages of doth bags over plastic bags during shopping?

## Sources of Energy Class 10 MCQs Questions with Answers

Sources Of Energy Class 10 MCQ Question 1.
Which of the following is a non-renewable source of energy?
(a) Wood
(b) Sun
(c) Fossil fuels
(d) Wind
(c) Fossil fuels

Explanation: Non-renewable sources are those sources that are present in a limited amount and once finished cannot be renewed again for millions of years.

Wood comes from trees, so it is a renewable source of energy. The Sun and wind are also renewable sources of energy but fossil fuels are non-renewable (conventional sources). Once they are used up, they can’t be renewed again, so we need to conserve them.

Towards Green Energy Class 10 MCQ Question 2.
In a hydropower plant:
(a) the potential energy possessed by stored water is converted into electricity
(b) the kinetic energy possessed by stored water is converted into potential energy
(c) electricity is extracted from water
(d) water is converted into steam to produce electricity

MCQ On Sources Of Energy Question 3.
Ocean thermal energy is due to:
(a) energy stored by waves in the ocean
(b) temperature difference at different levels in the ocean
(c) pressure difference at different levels in the ocean
(d) tides arising in the ocean

Source Of Energy Class 10 MCQ Question 4.
The major probLem in harnessing nuclear energy is how to:
(a) split nuclei?
(b) sustain the reaction?
(c) dispose off spent fuel safely?
(d) convert nuclear energy into electrical energy?

Class 10 Science Chapter 14 MCQ Question 5.
Which part of the solar cooker is responsible for the greenhouse effect?
(a) Coating with black coLour inside the box
(b) Mirror
(c) Glass sheet
(d) Outer cover of the solar cooker
(c) Gloss sheet

Explanation: Sotar cookers are covered with a glass plate which traps infrared radiations (heat) from sunlight and does not allow them to escape. In other words, we can say that it provides a greenhouse effect. Solar cookers achieve a higher temperature by using mirrors to focus the rays of the Sun.

Related Theory

The trapping of heat in the environment due to the presence of greenhouse gases like CO2, methane, water vapour etc. causes the greenhouse effect. This raises the temperature of Earth.

MCQs On Sources Of Energy Question 6.
The main constituent of biogas is:
(a) methane
(b) carbon dioxide
(c) hydrogen
(d) hydrogen sulfide
(a) methane

Explanation: Biogas is an excellent fuel as it contains up to 75% methane. It burns without smoke, leaves no residue like ash in wood. charcoal and coal burning. Its heating capacity is high. It is also used for lighting.

Sources Of Energy MCQ Question 7.
The power generated in a windmill:
(a) is more in the rainy season, since damp air would mean more air mass hitting the blades
(b) depends on the height of the tower
(c) depends on wind velocity
(d) can be increased by planting tall trees close to the tower

Source Of Energy MCQ Question 8.
Choose the correct statement:
(a) The Sun can be taken as an inexhaustible source of energy
(b) There is infinite storage of fossil fuel inside Earth
(c) Hydro and wind energy plants are non-polluting sources of energy
(d) Waste from a nuclear power plant can be easily disposed off

MCQ Of Sources Of Energy Class 10 Question 9.
In a hydroelectric power plant, more electrical power can be generated if waterfalls from a greater height because:
(a) its temperature increases
(b) larger amount of potential energy is converted into kinetic energy
(c) the electricity content of water increases with height
(d) more water molecules dissociate into ions

Ch 14 Science Class 10 MCQ Question 10.
The biggest source of energy on Earth’s surface is:
(A) Biomass
(C) Tides
(D) Winds

Sources Of Energy MCQ Class 10 Question 11.
Which is the type of system where the energy is harnessed by the heat accumulated on the surface of the water?
(a) Wind energy
(b) Wave energy
(c) Ocean thermal energy conversion
(d) Solar energy
(c) Ocean thermal energy conversion

Explanation: Absorption of heat from the sun by the seas and oceans, solar radiation causes ocean currents and moderate temperature gradients from the water surface downward especially in tropical waters.

MCQ Of Chapter 14 Science Class 10 Question 12.
The correct energy conversion taking place in a hydroelectric power plant is:
(a) Potential energy of water → Kinetic Energy of turbine → Electrical energy
(b) Potential energy of turbine → Kinetic Energy of water → Electrical energy
(c) Heat energy of water → Kinetic Energy of turbine → Electrical energy
(d) Potential energy of water → Heat Energy → Electrical energy

MCQ Questions On Sources Of Energy Class 10 Question 13.
Which of the following are non-conventional sources of energy:
(I) Wind energy
(II) Water
(III) Solar energy
(IV) Geothermal energy
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (II) and (IV)

Chapter 14 Science Class 10 MCQ Question 14.
Approximately what percentage of energy requirement in India is met by hydropower plants?
(a) 10 %
(b) 25 %
(c) 50 %
(d) 75 %
(b) 25 %

Explanation: A quarter or 25 % of the energy requirement in India is met by hydropower plants. But we are still largely dependent upon coal and petroleum for meeting our energy requirements.

Class 10 Sources Of Energy MCQ Question 15.
The table below lists the sources of energy and whether they are exhaustible or non-exhaustible. Select the row containing incorrect information:

 Source of energy Whether exhaustible or non- exhaustible (a) Fossil fuel Exhaustible (b) Wind Non-exhaustible (c) Water Exhaustible (d) Solar Non-exhaustible

Question 16.
Two fuels obtained from biomass are:
(a) Coal and biogas
(b) Petroleum and natural gas
(c) Charcoal and biogas
(d) Charcoal and natural gas
(c) Charcoal and biogas

Explanation: When wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and charcoal is left behind as the residue. Charcoal burns without flames is comparatively smokeless and has a higher heat generation efficiency. Similarly, cow-dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage are decomposed in the absence of oxygen to give biogas.

### Assertion Reasoning questions Class 10 Science Chapter 14

For the following questions, two statements are given one labeled Assertion (A) and the Other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 17.
Assertion (A): In a wind energy farm, a number of windmills are erected over a large area.
Reason (R): The output of a single windmill is quite small and cannot be used for commercial purposes.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.

Question 18.
Assertion (A): All exhaustible sources of energy are non-renewable.
Reason (R): Energy sources that cannot be regenerated are called renewable sources of energy.

(Competency Based Questions (CBQs))

Question 1.
Geothermal energy is the energy produced by the heat of molten rocks formed in the deeper hot regions of the earth’s crust. This energy is harnessed to generate electricity. When water is made to flow deep underground in the rocks it returns as steam (or hot water, which is later converted to steam) to drive a turbine on an electric power generator.
In India, exploration and study of geothermal fields started in 1970. The Geological Survey in India has identified 350 geothermal energy locations, in the country. The most promising of these is in Puga Valley of Ladakh. The estimated potential for geothermal energy in India is about 10000 MW. There are seven geothermal provinces in India namely the Himalayas, Sohna, West coast, Cambay, Son- Narmada-Tapi; Godavari and Mahanadi. Most power stations in India produce Alternating Current (A.C).
(A) What are geothermal energy hot-spots?
Though the total energy stored in the earth is very vast, but geothermal energy can be harnessed only in particular areas. The particular areas where geothermal energy can be harnessed are called geothermal hot spots.

(B) Name two countries, other than India, where power plants based on geothermal energy are operational.

(C) Name the phenomenon that explains the working of an electric generator.
Electromagnetic induction is the phenomenon that explains the working of an electric generator.

Explanation: An electric generator is a machine which converts mechanical energy into electrical energy. The phenomenon of electromagnetic induction can be seen as:

The phenomenon of generation of an electric current in a circuit from magnetic effects is called electromagnetic induction.

(D) State an important advantage of using AC over DC.
An important advantage of using AC over DC is that electric power can be transmitted over long distances without much loss of energy.

Related Theory
The frequency of AC in India is 50 Hz. DC always flows in one direction, whereas AC reverses its direction periodically. AC can also be changed to DC whenever required

Question 2.
Acid rain as the name suggests can be said to be the precipitation of acid in the form of rain in the simplest manner. Taj Mahal, one of the 7 wonders of the world, is Largely affected by acid rain.

Acid rain happens because:
(a) the Sun causes the heating of the upper layer of atmosphere
(b) the burning of fossil fuels releases oxides of carbon, nitrogen and sulphur in the atmosphere
(c) electrical charges are produced due to friction amongst clouds
(d) Earth atmosphere contains acids
(b) the burning of fossil fuels releases oxides of carbon, nitrogen and sulphur in the atmosphere

Explanation: The oxides of carbon, nitrogen and sulphur that are released on burning fossil fuels are acidic oxides. These lead to acid rain, which affects our water and soil resources.

Related Theory
The activities (polluting the atmosphere by industrial exhausts), as well as natural phenomena (emission of volcanos), cause acid rain due to the above mentioned oxides that are released.

Question 3.
Solar power in India is a fast developing industry. The country’s solar installed capacity reached 30.071 GW as of 31 July, 2019. India has the lowest capital cost per MW to install solar power plants. Solar electricity generation recorded nearly 3.4% of total utility electricity generation in January 2019. The following table shows Annual Solar Power Generation of the last six years.

 Year Solar Power Generation(TWh) 2013-14 3.35 2014-15 4.60 2015-16 7.45 2017-18 25.87 2018-19 39.27

Our country is lucky to receive solar energy for the greater part of the year. It is estimated that during a year India receives the energy equivalent to more than 5000 trillion kWh from the Sun.
(A) What are solar cells?
Solar cells are devices which convert Solar energy (Sun’s energy) directly into electricity. A solar cell is also known as a solar photovoltaic (SPV) cell.

Related Theory
A solar cell is made of element silicon. It consists of square piece of silicon. The electric power generated by a single solar cell is very small. So a number of cells are joined together to form a solar panel.

(B) How much voltage can be developed and how much electricity can be produced by one typical solar cell when exposed to the Sun?.
One typical cell produces a voltage of 0.5V-1V and can produce about 0.7 W of electricity when exposed to the sun.

Related Theory
Solar devices like solar cooker, solar geyser etc. also use solar energy but can be used only at certain times during the days. This limitation was overcome by combining solar cells in an arrangement called solar cell panel

(C) The future of power generation by solar energy is bright in India. Give reason.

(D) List two advantages of solar cells.
Advantages of solar cells: The solar cells

1. have no moving parts, require little maintenance and work satisfactorily without the use of any focusing device.
2. can be set up in remote and inaccessible area or very sparsely inhabited arons

Question 4.
Thermal power plants have been in operation since quite some time. Bharat Heavy Electricals (BHEL) has commenced civil works at 660 MW Sagardighi supercritical thermal power project in the state of West Bengal. BHEL is a manufacturer of power generation equipment with an installed base of over 1,90,000 MW power plant equipment globally.

The fuel used in thermal power plants is:
(a) water
(b) uranium
(c) biomass
(d) fossil fuels

Question 5.
Renewable energy sources such as wind energy are vital for the Indian economy, not only from the point of view of supply, but also from the perspective of environmental and social benefits. India is the world’s fifth largest wind-power producer and the largest windmill facilities in India are installed in Tamil Nadu. Muppandal is a small village of Tamil Nadu and one of the most important sites of wind-farm in the state. It uses wind from the Arabian Sea to produce renewable energy. The suitability of Muppandal as a site for wind farms stems from its geographical location as it has access to the seasonal monsoon winds.

The electrical generators used on wind turbines in sites like Muppandal, produce an output AC of 240 V and a frequency of 50 Hz even when the wind speed is fluctuating. A transformer may be required to increase or decrease the voltage so it is compatible with the end usage, distribution or transmission voltage, depending on the type of interconnection.
(A) State the principle behind electric generator.
The principle behind electric generator is Electromagnetic Induction- the pheno¬menon of producing current in a coil by changing the magnetic field associated with it.

(B) The output frequency of wind turbine is 50 Hz. What is meant by this statement?
The polarity of the output alternating current changes every $$\frac{1}{100}$$ seconds.

Alternately:
In 1 second the output (AC) completes 50 cycles.

(C) Why do you think Muppandal is at an advantageous position for this project?

(D) Based on the data represented in the graph below, which of the two cities A or B would be an ideal location for establishing a wind-farm and why?

City A

It is more suitable for a wind-farm as there is consistently high wind-speed in that city throughout the year.

Question 6.
A nuclear power plant is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a generator that produces electricity. As of 2018, the International Atomic Energy Agency reported there were 450 nuclear power reactors in operation in 30 countries around the world.

Nuclear power is the fifth-largest source of electricity in India after coal, gas, hydroelectricity and wind power. As of November 2020, India has 22 nuclear reactors in operation in 7 nuclear power plants, with a total installed capacity of 6,780 MW.

Which one of the following statements is not true about nuclear energy generation in a nuclear reactor?
(a) Energy is obtained by a process called nuclear fission.
(b) The nucleus of Uranium is bombarded with high energy neutrons.
(c) A chain reaction is set in the process
(d) In this process a tremendous amount of energy is released at a controlled rate.
(b) The nucleus of uranium is bombarded in the high energy neutrons.
Explanation: In a nuclear reactor, nuclear fission of nuclear fuel takes place to generate nuclear energy. Nuclear energy is released when nueleus of uranium is bombarded with low energy neutrons. Hence, this statement (b) is incorrect. All other three statements are correct.

Nuclear fission is the phenomenon of splitting of Uranium (heavy atom) into two medium weight nuclei. When it is bombarded with a slow neutron. A large amount of energy is released. In a nuclear reactor, nuclear fuel is a part of a self sustaining fission chain reaction that releases energy at a controlled rate.

Chain reaction:

The fission of an atom of uranium produces 10 million times the energy produced by the combustion of an atom of carbon from coal.

Question 7.
The Tehri dam is the highest dam in India and one of the highest in the World. The Tehri dam withholds a reservior of capacity 4.0 km3 and surface area 52 km2. It is used for irrigation, municipal water supply and the generation of 1000 MW of hydro electricity.
The Tehri Dam has been the object of protests. Environment activist Shri Sunder Lai Bahuguna led the ‘Anti Tehri Dam Movement” from 1980s to 2014. The protest was against the displacement of town inhabitants and environmental consequences of the weak ecosystem. The relocation of more than 1,00,000 people from the area has led to protracted legal bat over resettlement rights and ultimately resulted in the delayed completion of the project.
(A) How is hydropower harnessed?

(B) Define 1 MW.
1 mW is a unit for measuring power (megawatt)
1 mW = 1000 kW 1 kW = 1000 W 1 mW = 106 W

(C) Mention two disadvantages of constructing Tehri Dam.

1. Large ecosystems are destroyed when submerged under the water in dams.
2. The vegetation which is submerged rots under anaerobic conditions and release a large amount of methane gas which is a green-house gas.
3. Large areas of agricultural land is used.
4. It creates a problem of satisfactory rehabilitation of displaced people

(D) What happens when water from great heights is made to fall on blades of turbine?
When water from great heights is made to fall on blades of turbine, the potential energy of the water changes into kinetic energy which is transferred to the turbine. Moving turbine rotates the armature of a generator and kinetic energy of water changes to electricity.

Question 8.
Take two conical flasks and paint one white and the other black. Fill both with water. Place the conical flasks in direct sunlight for half an hour to one hour. Touch the conical flasks. You could also measure the temperature of the water in the two conical flasks with a thermometer.

Next, study the structure and working of a solar cooker and/or a solar water-heater, particularly with regard to how it is insulated and maximum heat absorption is ensured. Design and build a solar cooker or water- heater using low-cost material available and check what temperatures are achieved in your system.
(A) In the first activity, two conical flasks, one painted white and the other black, are filled with water and then placed in direct sunlight, for half an hour. Select the correct observation regarding their temperature:
(a) Both the conical flasks will be equally hot.
(b) The conical flask painted black will be hotter.
(c) The conical flask painted white will be hotter.
(d) The conical flask painted white will absorb more heat
(b) The conical flask painted black will be hotter.

Explanation: The conical flask painted black will be hotter as compared to the flask painted white as a black surface absorbs more heat as compared to a white or a reflecting surface under identical conditions.

(B) The parts of a box – type solar cooker is given below. Select the row containing incorrect information.

 Part Description (a) Black box An insulated metal, or wooden box which is painted white from the inside to radiate more heat. (b) Glass cover Made of two sheets of toughened glass held together in an aluminium frame. (c) Plane Mirror Plane mirror is fixed to the box with the help of hinges and it acts as a reflector (d) Cooking Containers A set of aluminium containers blackened from the outside are kept in the box

(C) The property used by solar cookers and solar water heaters is:
(a) A reflector absorbs more heat as compared to a white surface under identical conditions.
(b) Black surface reduces loss of heat by radiation.
(c) White surface absorbs more heat as compared to a reflecting surface under identical conditions.
(d) Black surface absorbs more heat as compared to a white or a reflecting surface under identical conditions.
(d) Black surface absorbs more heat as compared to a white or a reflecting surface under identical conditions.

(D) The purpose of a glass sheet fixed on the box of the solar cooker is:
(a) To focus sun’s radiations at one point.
(b) To absorb maximum heat of the sun’s rays.
(c) To prevent heat from escaping escape from the cooker box.
(d) To reflect sun’s rays towards the cooker box.

(E) Which of the following is not a limitation of solar cooker?
(a) Some solar cookers take longer to cook food than a conventional stove or an oven.
(b) Reduces carbon footprint by cooking without carbon dioxide-based fuels.
(c) It can be used only at certain time of the day.
(d) It cannot be used during nights and rainy days.
(b) Reduces carbon footprint by cooking without carbon dioxide-based fuels.

Explanation: As solar cooker uses only solar energy, there is no pollution caused as it does not use carbon dioxide based fuels and hence carbon footprint is reduced.

Question 9.
When Poorva visited Bengaluru along with her parents, she noticed that most houses had solar panels installed on their roof top. However, despite their ability to generate clean, green electricity, solar panels aren’t as commonplace as the could be. The main sticking point, of course, is price. Due to their need for relatively expensive semiconductor materials, conventional solar cells don’t yet have a price-efficiency combination that can compete with other sources of electricity. A conventional solar cell is made of a thin wafer of a semiconductor with a metallic electrode deposited on its rear side.

The values of voltage developed in a solar cell and power of a solar cell when exposed to electricity are given in the following table. Select the row containing the correct values:

 Voltage Developed in a Solar Cell Power Produced in a Solar Cell (a) 0.7 V 0.5-1.0 kW (b) 0.5-1.0 V 0.7 W (c) 5-10 V 0.7 kW (d) 1.5-2.0 V 7 W

(b) Voltage Developed in a Solar Cell: 0.5 -1.0 V; Power Produced in a Solar Cell: 0.7 W
Explanation: A typical solar cell develops a voltage of 0.5-1 V and can produce about 0.7 W of electricity when exposed to the Sun.

Question 10.
Discuss in class the question of what is the ultimate source of energy for bio-mass, wind and ocean thermal energy.
Gather information about various energy sources and how each one affects the environment.
Debate the merits and demerits of each source and select the best source of energy on this basis.
(A) The ultimate source of energy for bio¬mass is:
(a) Living organisms
(b) Sun
(c) Water
(d) Earth
(b)sun

Explanation: The ultimate source of energy for bio-mass is the sun as these fuels are plant and animal products and plants and animals ultimately depend on sun for their energy needs.

(B) Following statements are given below regarding wind energy and nuclear energy.
Select the incorrect statements:
(I) Wind energy does not contaminate the environment but nuclear energy may contaminate the environment.
(II) Efficiency of wind energy farms is less than that of nuclear plants.
(III) Wind energy farms can be set up anywhere whereas nuclear power plants can be set up only at specific locations.
(IV) Both are non-conventional sources of energy
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) (II), (III) and (IV)
(c) Both (III) and (IV)

Explanation: The wind energy farms can be set up only at specific locations where wind blows for the greater part of a year and the wind speed should also be higher than 15 km/

(C) Select the correct statement regarding different sources of energy:
(a) Geothermal energy makes use of steam trapped in rocks due to geological changes.
(b) Nuclear energy makes use of chemical reactions between different atoms to produce energy.
(c) Hydroelectricity makes use of gravitational pull of the moon on the spinning earth.
(d) Wave energy makes use of potential energy possessed by the waves.

(D) Out of coal, petroleum, solar energy and wind, minimum pollution is caused by:
(a) Coal
(b) Petroleum
(c) Solar energy
(d) Wind energy

(E) Which of the following factor does not affect the?
(a) Ease of extracting energy from that source.
(b) Economics of extracting energy from the source and efficiency of the technology available.
(c) Environmental damage that will be caused by using that source.
(d) Has less energy efficiency and more calorific value
(d) Has less energy efficiency and more calorific value

Explanation: All the above factors affect the choice of a particular source of energy.

Question 11.
Shaurya visited her paternal village after quite some time. She was pleasantly surprised to see that most of the houses had biogas chulhas at their place as a biogas plant was built by an NGO at the village.

Why is biogas considered an excellent fuel?

Question 12.
Wind power is one of the fastest-growing renewable energy technologies. Usage is on the rise worldwide, because costs are falling. Global installed wind-generation capacity onshore and offshore has increased by a factor of almost 75 in the past two decades, jumping from 7.5 gigawatts (GW) in 1997 to some 564 GW by 2018. Production of wind electricity doubled between 2009 and 2013, and in 2016 wind energy accounted for 16% of the electricity generated by renewables. Many parts of the world have strong wind speeds, but the best locations for generating wind power are sometimes remote ones. Offshore wind power offers tremendous potential.

The power curve of a wind turbine is a graph that indicates how large the electrical power output will be for the turbine at different wind speeds. At very low wind speeds, the torque exerted by the wind on the blades is insufficient to bring the turbine to rotate. The wind speed at which the turbine starts to generate electricity is called cut-in or start up wind speed and is typically between 3 and 4 m/s. Above the cut-in wind speed, there is sufficient torque for rotation, and power production increases before reaching a threshold. The lowest wind speed at which the nominal power is reached is called the rated (or nominal) wind speed and is typically between 12 and 17 m/s. The cut-off wind speed corresponds to the maximum wind speed a wind turbine can safely support while generating power and is usually about 25 m/s.

(A) Study the above power graph and select the row containing the correct information:

 Lowest Wind Speed at which the Nominal Power is Reached Wind Speed at which the Turbine Starts to Generate Electricity Maximum Wind speed a Wind Turbine can Safety Support while Generating Power (a) 12 m/s 3 m/s 22 m/s (b) 3 m/s 12 m/s 22 m/s (c) 3 m/s 22 m/s 12 m/s (d) 22 m/s 3 m/s 12 m/s

(a) Lowest Wind Speed at which the Nominal Power is Reached: 12 m/s ;
Wind Speed at which the Turbine Starts to Generate Electricity : 3 m/s ;
Maximum Wind speed a Wind Turbine can Safely Support while Generating Power: 22 m/s

Explanation: The lowest wind speed at which the nominaL power is reached is called the rated (or nominal) wind speed and is about 12 m/s.
The wind speed at which the turbine starts to generate electricity is called cut-in or start up wind speed and is about 3 m/s.
The maximum wind speed a wind turbine can safely support while generating power is the cut-off speed and is about 22 m/s.

(B) In a water-lifting pump:
(a) The up and down motion of windmill is converted to rotatory motion.
(b) The horizontal motion of windmill is converted to rotatory motion.
(c) The rotatory motion of windmill is converted to horizontal motion.
(d) The rotatory motion of windmill is converted to up and down motion.
(d) The rotatory motion of windmill is converted to up and down motion.

Explanation: A water pumping windmill is simple, and efficient. The blades of the windmill wheel catch the wind, which turns the rotor. The wheel assembly is attached to a hub assembly, which drives a geared mechanism that converts the rotary motion to an up-and-down motion. This motion drives a pump rod, up and down inside of a pipe in the well. A cylinder with a sealed plunger going up and down inside forces the water up the pipe.

(C) Select the correct statements regarding wind mills:
(I) The rotatory motion of the windmill is used to turn the turbine of the electric generator.
(II) The output of a single windmill is quite large and can be used for commercial purposes.
(III) A wind energy farm is a large area where a number of windmills are erected.
(IV) The energy output of each windmill in a farm is coupled together to get electricity on a commercial scale.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (III) and (IV)
(d) (II), (III) and (IV)

(D) Which of these processes explains the extraction of energy from wind to do work?
(a) conversion of mechanical energy of wind into kinetic energy
(b) conversion of kinetic energy of wind into mechanical energy
(c) conversion of mechanical energy of wind into potential energy
(d) conversion of potential energy of wind into mechanical energy

(E) The minimum wind speed to maintain the required speed of the turbine is:
(a) 15 km/h
(b) 18 km/h
(c) 20 km/h
(d) 25 km/h

Question 13.
Solar power in India is a fast developing industry. India is endowed with vast solar energy potential. About 5,000 trillion kWh per year energy is incident over India’s land area with most parts receiving 4-7 kWh per sq. m per day. Solar photovoltaics power can effectively be harnessed providing huge scalability in India. Solar also provides the ability to generate power on a distributed basis and enables rapid capacity addition with short lead times. Off-grid decentralized and low- temperature applications will be advantageous from a rural electrification perspective and meeting other energy needs for power and heating and cooling in both rural and urban areas. Solar energy has taken a central place in India’s National Action Plan on Climate Change with National Solar Mission as one of the key Missions. Recently, India achieved 5th global position in solar power deployment by surpassing Italy. Solar power capacity has increased by more than 11 times in the last five years from 2.6 GW in March,2014 to 30 GW in July, 2019.

The following graph shows annual solar power generation of the last seven years.

(A) ApproximateLy what percentage of solar energy incident on earth’s outer atmosphere reaches the earth’s surface?
(a)20%
(c)30%
(c)50%
(d)80%
(c) 50 %

Explanation: Only a small part of soLar energy reaches the outer layer of the earth’s atmosphere. Nearly half of it is absorbed while passing through the atmosphere and the rest reaches the earth’s surface.

(B) The average solar energy incident over India’s Land area is given in tabLe beLow.
Select the row containing the correct information:

 Solar Energy Incident over India’s Land Area per Year Average Solar Energy Incident per sq. m per Doy (a) 2500 billion kWh 40-70 Wh (b) 5000 trillion kWh 4-7 kWh (c) 500 trilLion kWh 4-7 Wh (d) 5000 billion kWh 0.4-0.7 kWh

(b) Solar energy incictent over India’s land Area per year: 5000 trillion kWh: Average solar Energy incident Sq.m per Days 4-7 kWh ”

Explanation: About 5,000 triLlion kWh per year energy is incident over India’s land area with most parts receiving 4-7 kWh per sq. m per day.

(C) Energy conversion taking place in solar cell is:
(a) Solar energy is converted to Chemical energy
(b) Chemical energy is converted to electrical energy
(c) Heat energy is converted to Light energy
(d) Solar energy is converted to electrical energy

(D) The advantages of using solar cells are given below. Select the incorrect statements:
(I) They have no moving parts.
(II) They make use of focusing devices for satisfactory performance.
(III) They can be set up in remote areas where laying of a power transmission line may be expensive.
(IV) Special grade silicon used in making solar cells are abundantly available
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (II) and (IV)
(d) Both (II) and (IV)

Explanation: Solar cells work quite satisfactorily without the use of any focusing devices. Silicon, which is used for making solar cells, is abundant in nature but availability of the special grade silicon for making solar cells is limited.

(E) The substance used for interconnection of cells in solar panel is:
(a) Silver
(b) Gold
(c) Platinum
(d) Copper

Question 14.
Sardar Sarovar Dam (SSD), on the Narmada river, is located in the village of Kevadia in the state of Gujarat. It is one of the largest and most controversial interstate, multipurpose river valley infrastructure development projects in the country. The Sardar Sarovar Project (SSP) also consists of auxiliary works and a 1,450 MW power complex.
SSP was estimated to have cost INR 400bn ($8bn) in 2010-2011, revised from the initial estimate of INR 64bn ($1.25bn) in 1988. It is part of the Narmada Valley Development Project, a major plan to generate power and supply water for drinking and irrigation to states of Gujarat, Madhya Pradesh and Maharashtra. The scheme was conceived by the late Sardar Vallabhbhai Patel in 1946¬1947. It envisages the construction of 30 major dams, 135 medium and 3,000 smaller dams along the river, with SSD being the largest of them all. They are expected to generate about 4,000 MW of power in total.

(A) In hydroelectric power plants:
(a) Kinetic energy is converted to potential energy
(b) Wind energy is converted to solar energy
(c) Solar energy is converted to wind energy
(d) Potential energy is converted to kinetic energy

(B) Hydroelectric power plant uses :
(a) Non-renewable source of energy
(b) Non-conventional source of energy
(c) Conventional source of energy
(d) Exhaustible source of energy
(c) Conventional source of energy

Explanation: Hydroelectric power plant uses water, which is a conventional source of energy and Hydro power plants convert the potential energy of falling water into electricity. It is a non-exhaustible source of energy as water in the reservoir would be refilled each time it rains.

(C) Given below are statements regarding problems associated with constructions of big dams.
Select the correct statements.
(I) The dams can be constructed only along the river course in plain areas.
(II) Large areas of agricultural land and human habitation are to be sacrificed as they get submerged.
(III) Large eco-systems are destroyed when submerged under the water in dams.
(IV) The submerged vegetation rots and produces large amounts of carbon dioxide, a green house gas.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (III) and (IV)

(D) The present installed capacity of the Sardar Sarovar Project is:
(a) 1.450 MW
(b) 1450 kW
(c) 1450 MW
(d) 4000 MW
(c) 1450 MW

(E) The table below lists the comparison between thermal power plant and hydro power plant. Select the row containing incorrect information:

 Thermal Power Plant Hydropower Plant (a) Fossil fuels are burned to produce steam which runs turbine The kinetic energy of water is used to run turbine (b) Set up near coal or oil fields Set up near oceans (c) Causes pollution Is pollution free (d) Does not affect ecosystem Affects ecosystem

(b) Thermal Power Plant: Set up near coal or oil fields; Hydropower Plant: Set up near oceans

Explanation: Thermal power plants are usually set up near coal or oil fields to reduce the cost of transportation of coal or petroleum. In order to produce hydel electricity, high-rise dams are constructed on the river to obstruct the flow of water and thereby collect water in larger reservoirs.

Question 15.
Nuclear energy can be used to create electricity, but it must first be released from the atom. In the process of nuclear fission, atoms are split to release that energy. A nuclear reactor, or power plant, is a series of machines that can control nuclear fission to produce electricity. The fuel that nuclear reactors use to produce nuclear fission is pellets of the element uranium. Nuclear energy produces electricity that can be used to power homes, schools, businesses, and hospitals. The first nuclear reactor to produce electricity was located near Area, Idaho. The Experimental Breeder Reactor began powering itself in 1951. The first nuclear power plant designed to provide energy to a community was established in Obninsk, Russia, in 1954.

(A) The table below lists the fuel, process involved and principle used for generating nuclear energy. Select the row containing the correct information:

(B) Which of the following statements regarding nuclear reactors designed for electric power generation are incorrect?
(I) In a nuclear reactor designed for electric power generation the nuclear fuel undergoes fusion.
(II) A self sustaining chain reaction takes place.
(III) Energy is released at an uncontrolled rate.
(IV) The released energy is used to produce steam and further generate electricity.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (I) and (III)

(C) In nuclear fission, a heavy nucleus such as Uranium is bombarded with:
(a) A slow moving neutron
(b) A fast moving neutron
(c) A slow moving proton
(d) A fast moving electron
(a) A slow moving neutron
Explanation: In nuclear fission, when a heavy nucleus such as Uranium is bombarded with a slow moving neutron, the nucleus splits into two or more lighter nuclei.

(D) The major hazard of nuclear power generation is:
(a) It produces lot of smoke
(b) Storage and disposal of spent fuels
(c) Limited availability of uranium
(d) Uncontrolled chain reaction

(E) Which of the following is not a reason for large scale use of nuclear energy being prohibitive?
(a) Risk of accidental leakage of nuclear radiation.
(b) High cost of installation of a nuclear power plant.
(c) Low risk of environmental contamination
(d) Limited availability of uranium.
(c) Low risk of environmental contamination

Explanation: Improper nuclear-waste storage and disposal result in environmental contamination which is one of the reasons for large scale use of nuclear energy being prohibitive.

Question 16.
Koyal was reading about harnessing the energy from the ocean. She read about the OTEC technology which generates electricity from turbines turned by steam produced from heating the warmer surface waters of the sea into steam. The steam is then condensed by the deeper colder waters which are pumped up from depths of around 1000 metres.

What is the operating principal in OTEC systems?
The OTEC or Ocean Thermal Energy Conversion systems work on the principle that there is a temperature difference between the water at the surface of the ocean is about 20 k warmer than the water at depths up to 2 km which is used to boil a volatile liquid whose vapours are then used to run the turbine of a generator.

Question 17.
Wind power is arguably one of the oldest human technologies. Today, wind power is symbolized in most people’s minds by a big, white, monolithic wind turbine. As we try to move into the post-carbon era, it’s worth remembering that only wind, nuclear, and solar have the same technical potential to provide energy as fossil fuels do today. Perhaps the face of future power generation won’t be huge smokestacks, but fields of wind turbines.

What are the factors which limit the use of wind energy?
The factors which limit the use of wind energy are that the wind energy farms can be established only at places where wind blows for the greater part of the year and wind speed should also be greater than 15 km/h.

Question 18.
Geothermal energy, form of energy conversion in which heat energy from within the earth is captured and harnessed for cooking, bathing, space heating, electrical power generation, and other uses.Heat from Eorths interior generates surface phenomena such as lava flows, geysers, fumaroles, hot spíings, and mud pots. The heat is produced mainly by the radioactive decay of potassium, thorium, and uranium ¡n Earth’s crust and mantle and also by friction generated along the margins of continental plates.

What are hot spots? How are they different from hot springs?
Hot spots are the regions in the earth’s crust where molten rocks formed in the deeper hot regions of the earth’s crust are pushed and trapped. Hot springs are the outlets on the surface of the earth from where hot water comes out.

Question 1.
Name two constituents of biogas.
The two constituents of biogas are:
(1) Methane
(2) Carbon dioxide
(3) Hydrogen
(4) Hydrogen sulphide

## Control and Coordination Class 10 MCQs Questions with Answers

Control And Coordination Class 10 MCQ Question 1.
The electrical impulse travels in a neuron from:
(a) Dendrite Axon → Axonal end → Cell body
(b) Cell body → Dendrite → Axon → Axonal end
(c) Dendrite → Cell body → Axon → Axonal end
(d) Axonal end → Axon → Cell body Dendrite
(c) Dendrite → Cell body → Axon → Axonal end

Explanation: The electrical impulse travels from the dendrite to the cell body, and then along the axon to its axonal end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.

Control And Coordination MCQ Question 2.
In a synapse, a chemical signal is transmitted from:
(a) The dendritic end of one neuron to the axonal end of another neuron.
(b) Axon to cell body of the same neuron.
(c) Cell body to the axonal end of the same neuron.
(d) The axonal end of one neuron to the dendritic end of another neuron.
(d) The axonal end of one neuron to the dendritic end of another neuron.

Explanation: The chemical signal is transmitted from axonal end of one neuron to the dendritic end of another nueron. This microscopic gap is called synapse.

MCQ On Control And Coordination Question 3.
In a neuron, the conversion of electrical signal to a chemical signal occurs at/in:
(a) Cell body
(b) Axonal end
(c) Dendritic end
(d) Axon

Class 10 Science Chapter 7 MCQ Question 4.
Which is the correct sequence of the components of a reflex arc?
(a) Receptors Muscles → Sensory neuron → Motor neuron → Spinal cord
(b) Receptors → Motor neuron → Spinal cord Sensory neuron → Muscle
(c) Receptors → Spinal cord → Sensory neuron → Motor neuron → Muscle
(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle
(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle

Explanation: A stimulus received by the receptors present on skin, is transmitted to the sensory neuron, which carries it to the central nervous system (the spinal cord and brain).

A motor neuron carries the message from the central nervous system to the effector which could be a muscle, a gland or both.

Related Theory
Nerve based pathway performed by an impulse from the receptor of stimulus to the effector organ is called the reflex arc. A reflex action is a nerve mediated automatic and spontaneous response to a certain stimulus without sonsulting the wilt of the individual coughing, sneezing, etc.

MCQ Of Control And Coordination Question 5.
Which of the following statements are true?
(I) Sudden action in response to something in the environment is called a reflex action.
(II) Sensory neurons carry signals from the spinal cord to muscles.
(III) Motor neurons carry signals from receptors to the spinal cord.
(IV) The path through which signals are transmitted from a receptor to muscle or a gland is called reflex arc.
(a) (I) and (II)
(b) (I) and (III)
(c) (I) and (IV)
(d) (I) (II) and (III)
(c) (I) and (IV)

Explanation: Reflex action is a sudden action in response to some stimuli in the environment. Reflex arc is the path through which signals are transmitted from a receptor to a muscle or a gland.

Class 10 Control And Coordination MCQ Question 6.
Which of the following statements are true about the brain?
(I) The main thinking part of bi in is the hindbrain.
(II) Centres of hearing, smell, memory, sight, etc. are located in the fore-brain.
(III) Involuntary actions like salivation, vomiting and blood pressure are controlled by the medulla in the hind brain.
(IV) Cerebellum does not control posture and balance of the body.
(a) (I) and (II)
(b) (I) (II) and (III)
(c) (II) and (III)
(d) (III) and (IV)

Control And Coordination MCQ With Answers Pdf Question 7.
The spinal cord originates from:
(a) Cerebrum
(b) Medulla
(c) Pons
(d) Cerebellum

MCQ Of Control And Coordination Class 10 Question 8.
The movement of shoot towards light is:
(a) Geotropism
(b) Hydrotropism
(c) Chemotropism
(d) Phototropism

Control And Coordination Class 10 MCQ With Answers Question 9.
The main function of abscisic acid in plants is to:
(a) Increase the length of cells
(b) Promote cell division
(c) Inhibit growth
(d) Promote growth of stem
(c) Inhibit growth

Explanation: Abscisic acid (ABA) is one example of a hormone which inhibits growth. Its effects include wilting of leaves.

Related Theory
Auxin is synthesized at the shoot tip, helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light.

Gibberellin helps in the growth of the stem.

Cytokinin promotes cell division, and it is natural then that they are present in greater concentration in areas of rapid cell division, as in fruits and seeds.

Abscisic acid inhibits growth. Its effects include wilting of leaves. It is also responsible for falling of senescent leaves.

Class 10 Chapter 7 Science MCQ Question 10.
Iodine is necessary for the synthesis of which hormone?
(b) Thyroxin
(c) Auxin
(d) Insulin
(b) Thyroxin

Explanation: Iodine is necessary for the thyroid gland to make the thyroxin hormone. Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodine is essential for the synthesis of thyroxin. In case iodine is deficient in our diet, there is a possibility that we might suffer from goitre. One of the symptoms in this disease is a swollen neck.

MCQ Questions For Class 10 Science Chapter 7 Question 11.
Choose the incorrect statement about insulin:
(a) It is produced from pancreas.
(b) It regulates growth and development of the body.
(c) It regulates blood sugar levels.
(d) Insufficient secretion of insulin will cause diabetes.

Control And Coordination Class 10 MCQs Question 12.
Select the mismatched pair:
(b) Testosterone – Testes
(c) Oestrogen – Ovary
(d) Thyroxin – Thyroid gland

Explanation: Adrenaline is secreted by the adrenal gland, whereas growth hormone is secreted by the pituitary gland.

Control And Coordination MCQ With Answers Question 13.
The growth of tendril in pea plants is due to:
(a) The effect of light.
(b) The effect of gravity.
(c) Rapid cell divisions in tendrillar cells that are away from the support.
(d) Rapid cell divisions in tendrillar cells in contact with the support.

Control And Coordination MCQ Class 10 Question 14.
The growth of pollen tubes towards ovules is due to:
(a) Hydrotropism
(b) Chemotropism
(c) Geotropism
(d) Phototropism

MCQs On Control And Coordination Question 15.
The movement of sunflower in accordance with the path of the sun is due to:
(a) Phototropism
(b) Geotropism
(c) Chemotropism
(d) Hydrotropism

Question 16.
Involuntary actions in the body are controlled by:
(a) Medulla in the forebrain
(b) Medulla in the midbrain
(c) Medulla in the hindbrain
(d) Medulla in the spinal cord
(c) Medulla in the hindbrain

Explanation: Medulla is a part of the hindbrain and controls involuntary action.

Question 17.
Which of the following is not an involuntary action?
(a) Vomiting
(b) Salivation
(c) Heartbeat
(d) Chewing
(d) Chewing

Explanation: The actions that are not under our direct control are known as involuntary actions. Vomiting, salivation and heartbeat are examples of involuntary action. These involuntary actions are controlled by the medulla in the hindbrain.

Question 18.
A doctor advised a person to take an injection of insulin because:
(a) His blood pressure was low.
(b) His heart was beating slowly.
(c) He was suffering from goitre.
(d) His sugar level in blood was high.
(d) His sugar level in blood was high.

Explanation: A person taking injections of insulin is suffering from diabetes. Insulin is a hormone which is produced by the pancreas. It helps in regulating blood sugar levels. If not secreted in proper amounts, the sugar level in the blood rises, causing many harmful effects.

Question 19.
The hormone which increases fertility in males is called:
(a) Oestrogen
(b) Testosterone
(c) Insulin
(d) Growth hormone
(b) Testosterone

Explanation: Testosterone is the male sex hormone necessary for sperm production. In addition to regulating the formation of sperms, testosterone brings changes in appearance seen in boys, at the time of puberty.

Question 20.
Which of the following endocrine glands is unpaired?
(b) Testes
(c) Pituitary
(d) Ovary

Question 21.
The junction between two neurons is called:
(a) Cell junction
(b) Neuromuscular junction
(c) Neural joint
(d) Synapse
(d) Synapse

Related Theory

• Synapse is the junction between two neurons.
• Cell junction is junction between neighboring cells.
• Neuromuscular junction allows delivery of impulses from neurons to other cells, like muscles cells/gland.

Question 22.
In humans, life processes are controlled and regulated by:
(a) Reproductive and endocrine systems.
(b) Respiratory and nervous systems.
(c) Endocrine and digestive systems.
(d) Nervous and endocrine systems.

Question 23.
Select the row containing incorrect information:

 Endocrine Gland The function of hormone secreted (a) Thyroid Regulates carbohydrate, protein and fat metabolism (b) Pituitary Regulates growth and development of the body (c) Pancreas Increasing blood sugar levels (d) Adrenal Increasing heart rate

(c) Endocrine Gland: Pancreas; Function of hormone – Increasing blood sugar levels

Question 24.
Look at the figure below and identify the structure labelled incorrectly:

(d) D-Dendrite

Explanation: Part labelled D is capillary and not dendrite, as dendrites receive nerve impulses.

Question 25.
Given below are four statements regarding endocrine glands and hoimones. Select the correct statements:
(I) Hormones are secreted by the endocrine glands.
(II) Some endocrine glands secrete hormones in response to other hormones.
(III) Hormones are required in large quantities.
(IV) Many hormones are controlled by some form of a feedback mechanism.
(a) Both (I) and (II)
(b) Both (I) and (III)
(c) (I), (II), and (III)
(d) (I), (II), and (IV)
(d) (I), (II), and (IV)

Explanation: Hormones are very potent substances, which means that very small amounts of a hormone may have profound effects on metabolic processes. Some endocrine glands secrete hormones in response to other hormones. The hormones that cause the secretion of other hormones are called tropic hormones. A hormone from gland A causes gland B to secrete its hormone. Many hormones are controlled by some form of a negative feedback mechanism, in this type of system, a gland is sensitive to the concentration of a substance that it regulates. A negative feedback system causes a reversal of increases and decreases in body conditions in order to maintain a state of stability.

Question 26.
Given below are four statements regarding the movement in plants.
Select the incorrect statements.
(I) Movement in plants happens at a point as the point of touch.
(II) The plants use electrical-chemical means to convey information from cell to cell.
(III) There are specialised tissues in plants for the conduction of information.
(IV) Plant cells change shape by changing the amount of water in them
(a) Both (I) and (III)
(b) Both (I) and (IV)
(c) Both (II) and (III)
(d) Both (II) and (IV)

Question 27.
The junction between two nerves is known as:
(a) Synapse
(b) Axon
(c) Dendrite
(d) Capillary
(a) Synapse

Explanation: The junction between two neurons is known as synapse. It is the site of transmission of nerve impulses between two nerve cells (neurons) or between a neuron and a gland or muscle cell (effector). A synaptic connection between a neuron and a muscle cell is called a neuromuscular junction.

Question 28.
The plant hormone that promotes dormancy m seeds and buds is:
(a) Auxin
(b) Gibberellin
(c) Cytokinin
(d) Abscisic acid
(d) Abscisic acid

Explanation: Abscisic acid is one example of a hormone which inhibits growth. Its effects include wilting of leaves and promoting dormancy in seeds and buds.

Question 29.
The secretion of which hormone leads to physical changes in the body when you are 10-12 years of age?
(a) Oestrogen from testes and testosterone from ovary.
(b) Oestrogen from adrenal gland and testosterone from pituitary gland.
(c) Testosterone from testes and Oestrogen from ovary.
(d) Testosterone from thyroid gland and Oestrogen from pituitary gland.

### Assertion Reasoning questions Class 10 Science Chapter 7

For the following questions, two statements are given: one labeled Assertion (A) and the other labeled Reason (R) Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Question 30.
Assertion (A): A growing plant appears to bend towards the direction of light.
Reason (R): The plant hormone auxin diffuses towards the shady side of the shoot.
(a) Both (A) and (R) are true and (R) is the correct explanation of the (A).

Question 31.
Assertion (A): Plants convey the acquired information from cell to cell.
Reason (R): Plants have specialized tissues for the conduction of information.
Select the correct answer to the above question from the codes (a), (b), (c) and (d) as given below:

Question 32.
Assertion (A): In animals, the brain is the main controlling center for responding to changes in their environment.
Reason (R): The thinking process of the brain is not fast enough in animals.
Answer: (d) (A) is false, but (R) is true.

Explanation: Reflex arcs have evolved in animals as the thinking process of the brain is not fast enough. Reflex action is any spontaneous, involuntary, and automatic response to a stimulus due to a change in our environment. For e.g. when a person touches a hot plate a sudden action leading to the withdrawal of hand occurs in a certain manner, this path of manner determines the reflex arc.

Reflex arcs have evolved in animals in order to take sudden and involuntary actions which are required in certain circumstances where emergency response is required to save the body from situations that may lead to danger.

(Competency Based Questions (CBQs))

Question 1.
The thyroid gland is a bibbed structure situated in our neck region. It secretes a hormone called thyroxine. Iodine is necessary for the thyroid gland to make thyroxine. Thyroxine regulates carbohydrate, protein and fat metabolism in the body. It promotes the growth of body tissues also. When there ¡s an excess of thyroxine ¡n the body, a person suffers from hyperthyroidism and if this gland Is underactive it results in hypothyroidism. Hyperthyroidism is diagnosed by blood tests that measure the levels of thyroxine and Thyroid Stimulating Hormone (TSH). Hypothyroidism ¡s caused due to the deficiency of iodine in our diet resulting in a disease called goitre. Iodised salt can be included in our diet ro control it.
(A) Where is the thyroid gland situated in our body?

(B) State the function of thyroxine in human body.
Thyroxine hormone is secreted by thyroid glands. Thyroxine plays vital roles in: increasing the basal metabolic rate regulating long bone growth. Increasing body’s seasitivity to hormone adrenaline, digestive function.

(C) What is hyperthyroidism?
Hyperthyroidism occurs when the thyroid gland produces excessive amount of hormone thyroxine

Related Theory
Hyperthyroidism means the thyroid gland is overactive and Overactive thyroid can sized up metabolism nervousness, anxiety, loss of mood swings etc.

(D) How can we control hypothyroidism?
We can control hypothyroidism by including iodised salt in our diet. Deficiency of iodine in our diet reduces the levels of ISH and a disease called goitre

Question 2.
While watching the TV show Master Chef Australia, Rima observed that the contestants were blindfolded and then asked to identify cubes of different fruits or food items by smelling and then by tasting them.

Which of the following statements is correct about receptors?
(a) Gustatory receptors detect taste while olfactory receptors detect smell.
(b) Both gustatory and olfactory receptors detect smell.
(c) Auditory receptors detect smell and olfactory receptors detect taste.
(d) Olfactory receptors detect taste and gustatory receptors detect smell.

Question 3.
Thyroid Stimulating Hormone (TSH) stimulates thyroid gland to produce thyroxine. Study the table given below.
Table: TSH Levels During Pregnancy

It is important to monitor TSH levels during pregnancy. High TSH levels and hypothyroidism can especially affect chances of miscarriage. Therefore, proper medication in consultation with a doctor is required to regulate/control the proper functioning of the thyroid gland.
(A) Give the full form of TSH.
Full form of TSH: Thyroid Stimulating Hormone.

(B) State the main function of TSH.
Thyroid stimulating hormone is produced by pituitary gland. Its main function is to regulate the production of hormones by the thyroid gland.)

Related Theory
A TSH test is a blood test that measures TSH i.e. how much of this hormone is present in blood. Thyroid gland is the largest gland endocrine gland, which is H-shaped present in the neck region. Thyroxine produced by thyroid gland regulates the metabolism of carbohydrates, proteins and fats.

(C) Why do TSH levels in pregnant women need to be monitored?

(D) A pregnant woman has TSH level of 8.95 mU/L. What care is needed for her?
A pregnant woman has TSH levels 8.95 m U/L which is very high in any of the three trimesters. A care is needed for her on regular basis to reduce the levels of TSH.

A regular test of TSH levels every 6-8 weeks should be done.
Proper medication in consultation with a doctor is required to regulate/control the proper functioning of the thyroid gland

Question 4.
Veer accidentally touched a thorn but quickly withdrew his hand. He later realized that he did this without even thinking about it! So, his reflexes were quite quick.

Reflex action is controlled by:
(a) Brain
(b) Spinal cord
(c) Peripheral Nervous System
(d) Autonomic Nervous System
(b) Spinal cord

Explanation: Reflex action is an involuntary and nearly instantaneous movement in response to a stimulus. A reflex action involves a very simple nervous pathway called a reflex arc. A reflex arc starts off with receptors being excited on sensing a stimulus. They then send signals along a sensory neuron to the spinal cord, where the signals are passed on to a motor neuron. Invertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. The spinal cord acts as the main centre for reflex actions. The spinal cord acts as a link between spinal nerves and the brain.

Question 5.
When Sanket went to a nearby farm with his friend, he found lots of mature fruits and Leaves lying on the ground. He tried to find out the reason behind this.

The substance that triggers the fall of mature leaves and fruits from plants is:
(a) Auxin
(b) Gibberellins
(c) Abscisic acid
(d) Cytokinin
(c) Abscisic acid

Explanation: Abscisic acid is one example of a hormone which inhibits growth. Its effects include wilting of leaves and fall of mature leaves and fruits from plants.

Question 6.
Study are table in which the levels of Thyroid Stimulating Hormone (TSH) in men are given and answer the questions that follow on the basis of understanding of the following paragraph and the related studied concepts.

men are at greater risk for developing abnormal TSH levels during instruction, white giving birth and after going through menopause. Found 5% of women in the United States have some kind of thyroid problem compared to 3% of men. Despite claims that high TSH increases risk for heart disease, a 2013 study found no link between high. TSH heart diseases. But a 2017 study showed that older women are specially at risk for developing thyroid cancer if they have high TSH calls along with thyroid nodules.
(A) A 35-year-old woman has TSH level 6.03 mll/L. What change should she bring in her diet to control this level?
The normal range of TSH level falls between 0.4 -4.0 m U/L. A 35 year old woman has TSH level 6.03 m U/L. 21 means she has higher level of TSH. Chance are that she may have an underactive thyroid. She should follow iodine rich diet.

Explanation: The deficiency of iodine in the diet of a person produces less thyroxine hormone. When a person will start taking iodine rich diet lies iodised salt, the thyroid gland will work actively to produce more thyroxine hormone.

(B) When do women face a greater risk of abnormal TSH level?
Women face a greater risk of abnormal TSH level during menstruation, while giving birth and after going through menopause.

(C) State the consequence of low TSH level.
The consequences of low TSH level:
(1) Body metabolism slows down
(2) Weight gain
(3) Forgetfulness
(4) Lack of concentration
(5) Faligne
(6) Depression etc. (Any two)

(D) Name the mineral that is responsible for synthesis of hormone secreted by thyroid gland.

Question 7.
Pranay’s father was suffering from diabetes since a long time. Apart from several dietary restrictions, he was given injections of insulin regularly.

Why are some patients of diabetes treated by giving injections of insulin?
Patients of diabetes have insufficient levels of insulin produced by pancreas and are therefore treated by giving injections of insulin. Insulin is a hormone which is produced by the pancreas and helps in regulating blood sugar levels. If it is not secreted in proper amounts, the sugar level in the blood rises causing many harmful effects.

Question 8.
A student was interested in knowing about various endocrine glands in human body, the hormones secreted by them and their functions. The figure below shows the endrocine glands in human males and females.

(A) The table below gives the names of some endocrine glands and their functions. Identify the row containing incorrect information:

 Name of Endocrine Gland Function (a) Thyroid Regulates carbohydrate, protein and fat metabolism in the body (b) Pituitary Regulates growth and development of the body (c) Pancreas Regulates levels of uric acid in blood (d) Testis Changes associated with puberty in males

(c) Name of Endocrine Gland : Pancreas;
Function : Regulates levels of uric acid in blood.

Explanation: Insulin is a hormone which is produced by the pancreas and helps in regulating blood sugar levels.

(B) The endocrine gland known as the master gland in human beings is:
(a) Pituitary gland
(b) Hypothalamus gland
(c) Pineal gland
(d) Thymus glands

(C) Identify which of the following state¬ments about thyroid gland is incorrect?
(I) Thyroid gland requires iodine to synthesize thyroxin.
(II) Deficiency of iodine in our diet may cause dwarfism.
(III) Thyroxin regulates protein, carbohydrates and fat metabolism in the body.
(IV) Iron is essential for the synthesis of thyroxin.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (III)
(d) Both (II) and (IV)

(D) Name the gland which secretes the growth hormone:
(a) Thyroid
(b) Pituitary gland
(c) Hypothalamus
(b) Pituitary gland

Explanation: Growth hormone is one of the hormones secreted by the pituitary and it regulates growth and development of the body. If there is a deficiency of this hormone in childhood, it leads to dwarfism.

(E) The dramatic changes in body features associated with puberty are mainly be¬cause of the secretions of:
(a) Oestrogen from testes and testos¬terone from ovary
(b) Oestrogen from adrenal gland and testosterone from pituitary gland
(c) Testosterone from testes and oes¬trogen from ovary
(d) Testosterone from thyroid gland and ostrogen from pituitary gland
(c) Testosterone from testes and ostrogen from ovary

Question 9.
Akriti’s grandfather complained of giddiness since past several days. Her father took her to the physician who checked his blood pressure and immediately prescribed medicines for hypertension.

Which part of the brain is responsible for involuntary actions?
The involuntary actions such as blood pressure, vomiting and salivation are controlled by the medulla in the hind-brain.

Question 10.
The neurons are cells with some special abilities. These cells get excited, because of the membranes that are in a polarised state. Each neuron has a charged cellular membrane, which means there is a voltage difference between the inside and the outside membrane.

Membrane potential is the difference in the total charge between the inside of the cell and the outside of the cell. Action potential is a short-term change in the electrical potential that travels across the neuron cell.

A nerve impulse is generated when the stimulus is strong. This stimulus triggers the electrical and chemical changes in the neuron. When a nerve impulse is generated, there is a change in the permeability of the cell membrane. The sodium ions flow inside and potassium ions flow outside, causing a reversal of charges. The cell is now depolarised. This depolarization results in an action potential which causes the nerve impulse to move along the length of the axon. This depolarization of the membrane occurs along the nerve. A series of reactions occur where the potassium ions flow back into the cell and sodium ions move out of the cell. This whole process again results in the cell getting polarised, with the charges being restored.

When the nerve impulse reaches the end of the axon, there are some chemicals released from the neurotransmitters. They diffuse across the synaptic gap, which is the small space present between the axon and the receptors. Nerve impulses can be transmitted either by the electrical synapse or the chemical synapse.

(A) From the statements given below regarding polarization and depolarization of neurons, select the row containing the correct information.

 Polarization of Neuron Depolarization of Neuron (a) The sodium ions flow into the cell and potassium ions move out of the cell. The sodium ions flow inside and potassium ions flow out-side (b) The potassium ions flow into the cell and sodium ions move out of the cell. The sodium ions flow inside and potassium ions flow out-side (c) The potassium ions flow into the cell and sodium ions move out of the cell. The potassium ions flow inside and sodium ions flow out-side (d) The potassium ions flow into the cell and sodium ions move out of the cell. The potassium ions flow inside and sodium ions flow out-side

(b) Polarization of Neuron: The potassium ions flow into the cell and sodium ions move out of the ceil.
Depolarization of Neuron: The potassium ions flow inside and sodium ions flow outside.

Explanation: When a nerve impulse is generated, there is a change in the permeability of the cell membrane. The cell gets depolarized when the sodium ions flow inside and potassium ions flow outside, causing a reversal of charges. The cell gets polarized when the potassium ion’s flow back into the cell and sodium ions move out of the cell.

(B) Four statements are given below. Select the incorrect statements.
(I) Nerve impulse is generated by the stimulus when a neuron is depolarized.
(II) Nerve impulse is generated by the stimulus when a neuron is polarized.
(III) The polarization of neuron results in an action potential.
(IV) The action potential causes the nerve impulse to move along the axon.
(a) Both (I) and (III)
(b) Both (II) and (IV)
(c) Both (I) and (IV)
(d) Both (II) and (III)
(c) Both (II) and (III)

(C) The part of a neuron which receives information from other neurons is/are :
(a) Cell body
(b) Axon
(c) Dendrites
(d) Myelin sheath

(D) The part of the neuron through which the impulse travels is:
(a) Axon
(b) Soma
(c) Dendrites
(d) Nucleus
(a) Axon

Explanation: Axon is a singLe prominent extension that emerges from the cell body and is responsible for conducting outgoing impulses away from the cell and towards other cells.

(E) Control and coordination in animals is provided by:
(a) Nervous tissues only
(b) Muscular tissues only
(c) Receptors
(d) Both nervous and muscular tissues

Question 11.
Sujay was watching a program when he found that several people of a particular region had swollen neck. He tried to gather more information regarding the probable cause of this disease.

Identify the disease they were suffering from and a possible cause.

Question 12.
Alzheimer’s disease is a progressive neurologic disorder that causes the brain to shrink (atrophy) and brain cells to die. Alzheimer’s disease is the most common cause of dementia – a continuous decline in thinking, behavioral and social skills that affects a person’s ability to function independently. The early signs of the disease include forgetting recent events or conversations. As the disease progresses, a person with Alzheimer’s disease will develop severe memory impairment and lose the ability to carry out everyday tasks. Common symptoms of Alzheimer’s disease include memory loss, language problems, and impulsive or unpredictable behavior. This happens because of a loss of connection between the nerve cells, or neurons, in the brain which means that information cannot pass easily between different areas of the brain or between the brain and the muscles or organs.

(A) Select the incorrect statement:
(a) Alzheimer’s is a type of dementia that causes memory loss.
(b) It occurs only in elderly people.
(c) The early signs of the disease include forgetting recent events or conversations.
(d) As the disease progresses, a person develops severe memory impairment and loses the ability to carry out everyday tasks.
(b) It occurs only in elderly people.

Explanation: Alzheimer’s disease can affect people of any age group and does not occur only in the elderly.

(B) In Alzheimer’s disease there is a loss of connection between the nerve cells, or neurons, in the brain because of which:
(I) Information cannot pass easily be-tween different areas of the brain.
(II) Information cannot pass easily be-tween the brain and the muscles or organs.
(III) Information cannot be acquired by the dendrite.
(IV) Gustatory and olfactory receptors stop working.
Select the correct statements:
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (II) and (IV)
(a) Both (I) and (II)

Explanation: In Alzheimer’s disease there is a loss of connection between the nerve cells, or neurons, in the brain because of which Information cannot pass easily between different areas of the brain and between the brain and the muscles or organs.

(C) Given below are some parts of the brain and their functions.
Select the row containing the correct information:

 Part of Human Brain Function (a) Hindbrain The sensation of feeling full during eating a meal (b) Cerebrum Controls involuntary actions such as salivation and vomitting (c) Medulla Controls intelligence and memory (d) Cerebellum Precision of voluntary actions

(d) Part of Human Brain: Cerebellum: Function: Precision of voluntary actions. Explanation: Sensation of feeling full during eating a meal is due to forebrain. Cerebrum controls intelligence and memory whereas the medulla controls involuntary actions such as salivation and vomiting.

(D) The part of human brain that is responsible for maintaining the posture and balance of the body is:
(a) Cerebrum
(b) Medulla
(c) Cerebellum
(d) Pons

(E) The main thinking part of the human brain is:
(a) Fore brain
(b) Mid brain
(c) Hind brain
(d) Cerebellum

Question 13.
Motor neuron disease (MND) is the name for a group of diseases that affects particular nerves known as motor nerves, or motor neurons. In MND, those neurons generate and die and slowly the muscles become weaker. This eventually leads to paralysis. It is also known as Lou Gehrig’s disease, amyotrophic lateral sclerosis or ALS. MND is a progressive disease that usually starts slowly and gets worse over time. Symptoms sometimes starting on one side of the body and then spreading. Usually, the first things people notice are:
(1) weakness in the hands and grip
(2) slurred speech
(3) weakness in the legs, and a tendency to trip
(4) weakness of the shoulder, making lifting diffcult
(5) cramps and muscles twitching
The graph below shows the age wise incidence of MND per 1 lakh of population for men and women.

This information, acquired at the end of the dendritic tip of a nerve cell, sets off a chemi¬cal reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. This is a general scheme of how nervous impulses travel in the body. A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or glands.
(A) Based on the passage above, select the correct statements regarding Motor Neuron Diseases (MND):
(I) MND incidence is higher in men than women.
(II) MND affect sensory neurons.
(III) MND is a progressive disease that usually starts slowly and gets worse over time.
(IV) MND may eventually lead to paral¬ysis as muscles become weaker.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) (I), (III) and (III)
(d) (I), (III) and (IV)
(d) (I), (III) and (IV)

Explanation: Motor Neuron Diseases (MND) affects motor neurons and not sensory neurons.

(B) Select the row containing the incorrect information:

 Type or Part of Neuron Function (a) Dendrites These carry signals in the form of electrical impulses away from the cell body (b) Sensory Neuron These are found in receptors such as the eyes, ears, tongue and skin, and carry nerve im¬pulses to the spinal cord and brain. (c) Motor neuron These are found in the central nervous system (CNS) and control muscle movements. (d) Relay neuron Relay neurons are found in the brain and spinal cord and allow sensory and motor neurons to communicate.

(a) Type or Part of Neuron: Dendrites: function: These are found in receptors such as the eyes, ears, tangue and skin and cavry nerve in pulses to the spinal cord and brain.

Explanation: The dendrites receive signals from other neurons or from sensory receptor ceLls. The dendrites are typically connected to the cell body, which is often referred to as the ‘control centre’ of the neuron, as it contains the nucleus. The axon is a long slender fibre that carries nerve impulses, in the form of an electrical signal known as action potential, away from the cell body towards the axon terminals, where the neuron ends. Most axons are surrounded by a myelin sheath (except for relay neurons) which insulates the axon so that the electrical impulses travel faster along the axon.

(C) The motor neurons:
(a) Are found in receptors
(b) Are found in the brain and spinal cord
(c) Are found in the Central nervous system
(d) Carry impulses to the spinal cord and brain

(D) In the diagram above, the parts marked A and B are:
(a) Sensory neuron and motor neuron respectively
(b) Sensory neuron and relay neuron respectively
(c) Motor neuron and relay neuron respectively
(d) Motor neuron and sensory neuron respectively

(E) In the diagram above, the motor neuron is labelled as:
(a) A
(b) B
(c) C
(d) D
(c) C

Explanation: The motor neuron carries response from the spinal cord to the effector organs.

Question 14.
The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of the nerves and ganglia outside the brain and spinal cord. The main function of the PNS is to connect the CNS to the limbs and organs, essentially serving as a relay between the brain and spinal cord and the rest of the body.

In its simplest form, a reflex is viewed as a function of an idealized mechanism called the reflex arc. The primary components of the reflex arc are the sensory-nerve cells (or receptors) that receive stimulation, in turn connecting to other nerve cells that activate muscle cells (or effectors), which perform the reflex action.

A reflex arc is a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This allows for faster reflex actions to occur by activating spinal motor neurons without the delay of routing signals through the brain. The brain will receive the sensory input while the reflex is being carried out and the analysis of the signal takes place after the reflex action.

(A) Afferent neurons carry nerve impulses from
(a) CNS to muscles
(b) CNS to receptors
(c) receptors to CNS
(d) effector organs to CNS
(c) receptors to CNS

Explanation: The afferent neurons carry nerve impulses from the receptors to the central nervous system, whereas the efferent neurons carry impulses from the CNS to the effector organs.

(B) A neuron that carries information from the peripheral nervous system to the central nervous system is
(a) afferent neuron
(b) efferent neuron
(c) both
(d) none

(C) Which of these illustrate a reflex arc?
(a) Brain → Spinal cord → Muscles
(b) Muscles → Receptor → Brain
(c) Muscles → Spinal cord → Brain
(d) Receptor → Spinal cord → Muscles
(d) Receptor → Spinal cord → Muscles

Explanation: Reflex arc does not involve the brain. Infact it has evolved in higher animals as the thinking process of brain is not fast enough.

(D) Given below are the parts of the nervous system and their functions. Iden¬tify the row containing incorrect information:

 Part Function Peripheral Nervous System Consists of sensory organs Central Nervous System To organize and analyze information received Afferent Neurons Carry signals to the brain and spinal cord Efferent Neurons Carry neural impulses away from the central nervous system and toward muscles

(E) Select the correct statements:
(I) The PNS facilitates communication between the CNS and other parts of the body.
(II) The PNS consists of cranial nerves and spinal nerves
(III) The cranial nerves arise from the spinal cord.
(IV) The CNS carries signals to the brain and spinal cord.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (III) and (IV)
(d) Both (III) and (IV)

Explanation: The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system consisting of cranial nerves arising from the brain and spinal nerves arising from the spinal cord.

Question 15.
Plant hormones are among the most important biochemicals affecting plant growth and yield production under different conditions, including stress. Plant hormones include auxin, abscisic acid, ethylene, gibberellins, cytokinins, salicylic acid, strigolactones, brassinosteroids, and nitrous (nitric) oxide. Plant functioning under stress is affected by plant hormones, which can help the plant to tolerate the environmental stresses. Tropism is the type of plant movement, that is achieved by growth and responsible to directional light The movement is due to the action of auxin inside the plant part. Normally, phototropism, geotropism, hydrotropism and thigmotropism can be identified.
Within the above tropisms, the response of shoot tips are quite different from that of root tips. The basic difference is in the concentration they secreted. The level of auxin secreted from shoot tips is always on the ascending arm of the graph of response. But for the root tips, on the descending arm. Then, their responses become the opposite. The following graph shows the fact.

Auxin Concentration (Parts Per Milion)
Nb Logarithmic Scale For Auxin Concentration

(A) Observe the graph above and select the correct statements.
(I) Lower concentration of auxins decrease the growth of roots.
(II) Shoot growth requires greater concentrations of auxins as compared to the growth of roots.
(III) The application of very high concentration of auxin inhibits the growth of shoots directly.
(IV) The response of roots to auxin can thus be represented by an optimum curve with the peak at very low concentration.
(a) Both (I) and (III)
(b) Both (II) and (III)
(c) (I), (III) and (IV)
(d) (II), (III) and (IV)
(d) (II), (III) and (IV)
Explanation: Lower concentrations of auxins increases the growth of roots.

(B) The table below lists few plant hormones and their functions. However, one row contains incorrect information. Select the row containing incorrect information.

 Name of the plant hormone Function (a) Auxin Promotes cell elongation (b) Gibberellin Promotes seed germination and stem growth (c) Cytokinin Inhibits cell division (d) Abscisic acid Maintains seed dormancy

(c) Name of plant hormone: Cytokinin: Function: Inhibits cell division

Explanation: Cytokinin is a plant hormone that promotes cell division, and they are present in greater concentration in areas of rapid cell division, such as in fruits and seeds.

(C) Plant roots exhibit:
(a) Positive geotropism
(b) Negative geotropism
(c) Positive chemotropism
(d) Negative hydrotropism

(D) Which of the following plant hormone is responsible for seed germination?
(a) Auxin
(b) Gibberellin
(c) Ethylene
(d) Abscisic acid

(E) The hormone that is a growth inhibitor is:
(a) Auxin
(b) Abscisic acid
(c) Cytokinin
(d) Gibberellin
(b) Abscisic acid

Explanation: Abscisic acid is one example of a hormone that inhibits growth. Its effects include wilting of leaves.

Question 1.
Which one appears more accurate and why?

(A) is more appropriate as shoots are negatively geotropic and roots are positively geotropic. Hence, shoots grow upwards and roots grow downwards.

Related Theory
The roots of a plant always grow downwards while the shoots usually grow upwards and away from the earth. This upward and downward growth in response to the gravity pull is known as geotropism.

Question 2.
Name the two components of central nervous systems in humans.

Question 3.
How is the spinal cord protected in the human body?
Spinal cord is enclosed in a bony cage called the vertebral column.

Question 4.
A potted plant is made to lie horizontally on the ground. Which part of the plant will show (a) positive geotropism?

Question 5.
Name any two types of tropism.
Phototropism and geotropism.

Question 6.
Name the hormone that helps in regulating level of sugar is our blood. Name the gland that is secreted.
Insulin helps in regulating blood sugar level. This hormone is secreted by the pancreas gland.

Question 7.
Give an example of a plant hormone that promotes its growth. Where it is synthesized?

Question 8.
Mention the function of adrenaline hormone.
The function of adrenaline hormone is to regulate blood pressure, heartbeat breathing rate, carbohydrate metabolism and mineral balance in the body.

Question 9.
State the function of:
(A) gustatory receptors, and
(B) olfactory receptors