Here we are providing Class 11 Physics Important Extra Questions and Answers Chapter 1 Physical World. Important Questions for Class 11 Physics with Answers are the best resource for students which helps in Class 11 board exams.

Class 11 Physics Chapter 1 Important Extra Questions Physical World

Physical World Important Extra Questions Very Short Answer Type

Question 1.
Name that branch of science that deals with the study of Earth.
Answer:
Geology.

Question 2.
Name that branch of science that deals with the study of stars.
Answer:
Astronomy.

Question 3.
Name the scientist and the country of his origin whose field of work was elasticity.
Answer:
Robert Hook, England.

Question 4.
The word “Physics” comes from a Greek word. Name the word.
Answer:
The word is ‘fuses meaning ‘Nature’.

Question 5.
The word science has come from a Latin verb. Name the verb.
Answer:
The name of the Latin verb is ‘Scientia’.

Question 6.
What is the meaning of the verb ‘Scientia’?
Answer:
To ‘know’

Question 7.
Name the scientist and the country of his origin who received the Nobel Prize for his work on molecular spectra.
Answer:
C.V. Raman, India.

Question 8.
What is the most incomprehensible thing about the world?
Answer:
It is comprehensible.

Question 9.
Name a great scientist who gave the following comment on science.
“Science is not just a collection of laws, a catalog of unrelated facts. It is a creation of the human mind, with its freely invented ideas and concepts.”
Answer:
Albert Einstein.

Question 10.
Which famous philosopher gave the following comments on science?
“We know very little and yet it is astonishing that we know so much, and still more astonishing that so little knowledge of science can give so much power.”
Answer:
Bertrand Russel.

Question 11.
Who discovered the electron?
Answer:
J.J. Thomson.

Question 12.
Who discovered neutron?
Answer:
James Chadwick.

Question 13.
Who gave the general theory of relativity?
Answer:
Albert Einstein.

Question 14.
Who proposed the wave theory of light?
Answer:
Huygen.

Question 15.
Name four physics devices widely used in medical diagnosis.
Answer:

  1. X-rays,
  2. Ultrasound,
  3. Stethoscope,
  4. Microscope.

Question 16.
Name Indian-born scientist who received Nobel Prize for his discoveries in astronomy.
Answer:
S. Chandra Shekhar.

Question 17.
Metaphysics is a science that is concerned with what?
Answer:
Supernatural .events.

Question 18.
Which science is considered to be the mother of all sciences?
Answer:
Physics.

Question 19.
Name the discovery made by S.N. Bose.
Answer:
Bose-Einstein Statistics.

Question 20.
Name the scientist and the country of his origin whose field of work was ‘cosmic rays’.
Answer:
Hess, Austria.

Question 21.
What are the meaning of the Sanskrit word ‘Vijnan’ and the Arabic word ‘Ilm’?
Answer:
Knowledge.

Question 22.
Name the Sanskrit equivalent word of Physics.
Answer:
Bhautiki.

Question 23.
Name the field of Physics in which India was a leading country in the sixties.
Answer:
Cosmic rays.

Question 24.
Who discovered X-rays?
Answer:
W. Roentgen.

Question 25.
Which electronic media can help in eradicating illiteracy in India?
Answer:
Television.

Question 26.
Name the technology based on the amplification of light by population inversion?
Answer:
Laser.

Question 27.
Who discovered nuclear forces?
Answer:
H. Yukawa.

Question 28.
To which country he belonged?
Answer:
japan.

Question 29.
Who discovered Radium?
Answer:
Pierre Curie and Marie Curie.

Question 30.
Name the discovery made by W. Roentgen.
Answer:
X-rays.

Question 31.
What has been said by P.A.M. Dirac regarding physics in relation to society?
Answer:
P.A.M. Dirac said, “It is more important to have beauty in the equations of physics than to have them agree with experiments.”

Question 32.
What did Issac Newton say to measure the degree of impact of science on society?
Answer:
He said “Nature is pleased with simplicity, and affects not the pomp of superfluous causes.

Question 33.
What Neils Bohr said regarding science in relation to society?
Answer:
He said “The task of science is both to extend the range of our experience and to reduce it to order.

Question 34.
Name a few Indian physicists who have made significant contributions in the field of physics.
Answer:
C.V. Raifiaq, S. Chandra Shekhar, S.N. Bose, Homi J. Bhabha, and Meghnath Saha.

Question 35.
Name the scientific principle on which airplane works.
Answer:
Bernoulli’s theorem.

Question 36.
Name the scientific principle on which radio and T.V. works.
Answer:
Propagation of electromagnetic waves.

Question 37.
Name the scientific principle upon which laser works.
Answer:
Amplification by a process called population inversion.

Question 38.
Name the technology which works on the scientific principle “Newton’s second and third laws of motion”.
Answer:
Rocket propulsion.

Question 39.
Name the forces which are of nuclear origin.
Answer:
Strong forces.

Question 40.
What is Physics?
Answer:
It is that branch of science which deals with nature and natural phenomena.
Or
It is that branch of physical science that is to seek out and understands the basic laws of nature upon which all physical phenomena depend. It has brought to us deeper and deeper levels of understanding nature.

Question 41.
What is Science?
Answer:
It is defined as the systematic study of physical phenomena.

Question 42.
What are Biological Sciences? Give three examples.
Answer:
Those sciences which deal with living things are called Biological Sciences, e.g. Zoology, Botany, Ornithology.

Question 43.
What are Physical Sciences? Give a few examples.
Answer:
They ate defined as the sciences which deal with non-living things,
e.g. Physics, Chemistry, Astronomy, Astrology, Geology, Geography, Oceanology.

Question 44.
Define Theory.
Answer:
It is defined as the behavior of physical systems explained in terms of a set of a minimum number of laws.

Question 45.
What do you understand by the term scientific method?
Answer:
The systematic observations, logical reasoning, model-making, and theoretical prediction form the scientific method.

Question 46.
Name the scientific principle on which electric generator works.
Answer:
Electromagnetic induction (E.M.I.).

Question 47.
Name the technology which works on the scientific principle ‘Nuclear Fission’.
Answer:
Nuclear Reactor.

Question 48.
Name the technology which works on the scientific principle “Digital logic of electronic circuits”.
Answer:
Calculators and computers.

Question 49.
Name the scientific principle upon which the working of cyclotron defends.
Answer:
The motion of charged particles under electric and magnetic fields.

Question 50.
Name the. scientist and his country who discovered wireless1 telegraphy.
Answer:
G. Marconi, Italy.

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Physical World Important Extra Questions Short Answer Type

Question 1.
Differentiate between Biological and Physical sciences?
Answer:

Biological Sciences

Physical Sciences
(i) They deal with living things. (i) They deal with non-living things.
(ii) The study of the biological specimens is conducted at the molecular level. (ii) The study of matter is conducted at atomic or ionic levels i.e. at much smaller levels.

Question 2.
What is the relation between Physics and Technology?
Answer:
Broadly speaking, physics and technology both constitute science. Physics is the heart and technology is the body of science.

The application of the principles of physics for practical purposes becomes technology, e.g.

  1. Airplanes fly on the basis of Bernoulli’s theorem.
  2. Rockets propulsion is based on Newton’s second and third laws of motion.
  3. The generation of pow%r from the nuclear reactor is based on the phenomenon of controlled nuclear fission.
  4. Lasers are based on the population inversion of electrons and so on. Thus, we can say that to some extent technology is applied to Physics.

Question 3.
What is the relation between Physics and society?
Answer:
Most of the development made in Physics has a direct impact on society, e.g.

  1. Exploration of new sources of energy is of great importance to society.
  2. Rapid means of transport are no less important for society.
  3. society has-been enriched due to the advances in electronics, lasers, and computers.
  4. The development of T.V., radio, satellites, telephone, the telegraph has revolutionized the means of communications which have a direct impact on society and so on.

Question 4.
Is Science on speaking terms with humanities?
Answer:
Yes, there is a deep relation between the development of humanity on account of science. Many socio-economic, political, and ethical problems are being tackled and solved by science. Science has greatly helped in developing art and culture. Many musical instruments have been developed due to the theories in Physics. The steam engine is inseparable from the industrial revolution which had a great impact on human civilization.

Question 5.
What is the relation between Physics and Technology?
Answer:
The interplay between physics and technology is the basic to the progress of science which is ever dynamic. Laws in waves and oscillation opened several technological fields which include telescopy, ultrasounds, microscopy, X-rays, and laser. Powerhouses, big cranes, healing devices, etc. work on the principle of electromagnetism. Atomic energy and nuclear weapons are on account of fission. Similarly, Radar, television, the internet, etc. are all based on simple laws of physics. So until there is no theory i.e. physics, there can be no experiment i.e. technology. Hence both are deeply related.

Question 6.
Is Physics more of a philosophy or more of a mathematical science?
Answer:
Physics is not a purely abstract science devoid of philosophy. Physicists are natural philosophers and Einstein is an example to quote. So Philosophy has provided the backbone to Physics.

Question 7.
Define Biophysics.
Answer:
It is defined as the understanding of biological processes based upon the principles of Physics. For example, spectroscopic techniques are used to study the constitution of biological molecules and disorders in them. Laws of thermodynamics are used to explain various biological activities of predators and also the activities of molecules.

Hence the application of Physics to bioscience is now well known to all of us.

Question 8.
Define Technology?
Answer:
It is defined as the study of newer techniques of producing machines, gadgets, etc. by using scientific discoveries and advancements. It is largely dependent on Physics.

Question 9.
Has imagination any role in Physics?
Answer:
One of the definitions of Physics says that “It is the science-based on imagination and intuition which can be tested experimentally and mathematically.” Thus, imagination has a great role in the development of physics. Schrodinger, De-Broglie, Heisenberg, and most of the other scientists who were physicists were great imaginers.

Question 10.
Name a few aspects of your daily life in which you rely on the simplicity of nature.
Answer:
Laws of Physics represent the nature in simplest form. We face nature in many ways in our daily life. For example, we work, walk, write, talk and stand on our feet, and so on. The natural way of taking bath, chewing food, etc. can easily be understood in terms of simple laws of science. Even though actions like swimming, running, and playing may be complex but the underlying laws of nature are quite simple such as Newton’s laws, friction, etc.

Question 11.
The physicists think at a level far higher than a normal individual. Explain.
Answer:
For everyone to become a leader in his field, he has to think for a higher level than an ordinary person. This is more so for the case of physicists as the technological development meant for uplifting the living condition of mankind is highly dependent on the farsightedness of the physicists in particular. He must think at a level that is philosophical and mathematically quantifying so that they can visualize the requirement of people is quite advance.

Question 12.
Name a few wartime and maritime applications of Physics.
Answer:
(a) Wartime: The wartime applications are Bombs, nuclear weapons, jet fighter bombers, missiles, ships, radar, sonar, wireless communications, transportation, and electronics.

(b) Maritime: The maritime application of physics is Navigation of ships, tankers, airplanes, T.V., radio, and music system, etc.

Question 13.
Name five Indian scientists and the field of their work.
Answer:
Following are the five Indian Scientists and the field of their work:

Name Field of work
(1) C.V. Raman Raman effect (Scattering of light by molecules)
(2) S. Chandrashekar Theory of Black Hole
(i.e. structure and evolution of stars)
(3) J.C. Bose E. M. Waves
(4) S.N. Bose Bose-Einstein statistics
(5) H.J. Bhabha Cosmic rays

Question 14.
Who invented:
(i) Computer
Answer:
Charles Babbage

(ii) Transistor,
Answer:
J. Bardeen

(iii) Electric bulb and Telegraphy,
Answer:
A. Edison

(iv) Radar,
Answer:
Appleton

(v) Wireless telegraphy,
Answer:
Marconi

(vi) Telephone.
Answer:
Graham Bell.

Question 15.
Name the theories given by the following:
(i) Neil Bohr
Answer:
Theory of atomic structure

(ii) Lawrence,
Answer:
Cyclotron

(iii) Henry Becquerel,
Answer:
Natural radioactivity

(iv) Galileo,
Answer:
Principle of Inertia

(v) Bragg,
Answer:
Crystal structure by X- rays

(vi) Abdus Salam,
Answer:
Unified Field Theory

(vii) Millikan.
Answer:
Charge on an electron.

Question 16.
Give the nationality of the following scientists:
(i) Van der Waals,
Answer:
Dutch

(ii) Curie,
Answer:
French

(iii) Yukawa,
Answer:
Japanese

(iv) Galileo,
Answer:
Italian

(v) Michelson,
Answer:
U.S.A. (American)

(vi) Heisenberg,
Answer:
German

(vii) Archimedes,
Answer:
Greek

(viii) Maxwell,
Answer:
Scottish

(ix) Cavendish,
Answer:
English

(x) Hubble.
Answer:
Austrian.

Question 17.
List the Various gadgets you use in your house.
Answer:
The following are the gadgets commonly used in our house:

  1. Pressure Cooker
  2. Electric light
  3. Tube light
  4. Electric fan
  5. Water cooler
  6. Refrigerator
  7. Washing machine
  8. Gas stove
  9. Electric iron
  10. Mixi
  11. Geyser
  12. Electric motor.

Question 18.
Write the physical principle upon which the working of the gadgets mentioned in the above question is based.
Answer:
These are based on the following physical principles:

  1. The boiling point rises with the increase in pressure.
  2. Light is produced when the current is passed through a given resistor.
  3. Light is emitted when an electric discharge is passed through the gas.
  4. A rotating magnetic field is produced on passing current which notates the motor.
  5. Due to evaporation of water, cooling in the air which is being forced out by the fan is produced.
  6. On absorbing heat from the surroundings, compressed volatile liquid on sudden expansion causes cooling.
  7. Current produces a rotating magnetic field that operates the motor.
  8. Heat is produced due to the burning of L.P.G.
  9. It works on the principle of heating effect of electric current.
  10. Torque is produced on the coil due to the electric current passed through it, hence it rotates.
  11. Current shows the heating effect when passed through the conductor.
  12. It rotates due to the torque produced on the coil on passing an electric current through it.

Question 19.
Name one Scientist each from the following countries who have won Nobel Prize.
(a) Japan
Answer:
H. Yukawa

(b) England
Answer:
Janies Chadwick

(c) India
Answer:
C.V. Raman

(d) The U.S.A.
Answer:
K. Feynman

(e) Germany.
Answer:
Max. Plank.

Question 20.
How Darwin showed that scientific themes are at once simple even though phenomena in nature may be complex.
Answer:
Darwin found a simple basis for the origin of species and descent of man which is “Living things change producing descendants with different characteristics in a process that has been going on for as long as there has been life” by taking a large number of observations on the theory of evolution while onboard ship.

Question 21.
Illustrate by an example the beauty of a Scientific Theory.
Answer:
The theory proposed by Darwin was opposed by the church and now we have new discoveries such as selfish genes and punctuated equilibria but Darwin’s basic theory still holds. This is the beauty of Davin’s theory of evolution.

Question 22.
In science sometimes we observed certain phenomena experimentally but are unable to give a logical equation or theory for that sometimes, it also happens that we have a scientific theory supported by’ mathematical formulation yet are unable to test it immediately. Site one such example.
Answer:
Einstein worked to establish a relation between the energy and mass of the body. He was of the view that these are the two sides of the same coin or two facts of the same physical quantity. He succeeded when he gave his mass-energy equation E = mc2. But its experimental verification came 40 years later in 1945 when the atomic bomb was exploded over Japan.

Question 23.
Why do we call physics an exact science? What is the aim of science?
Answer:
Physics is called exact science because it is based on the measurement of fundamental quantities.
The main aim of science is to find the truth behind the various processes taking place in the universe.

Question 24.
How science has helped in solving the food problem in several countries?
Answer:
Science has helped in solving food problem in the following ways:
(a) It has given improved and new agricultural implements.
(b) Science has improved the quality of seeds by genetic engineering.
(c) High-yielding hybrid varieties of grains have been developed. Some easily reaping varieties have also been developed and grown.
(d) Use of pesticides and insecticides has saved crops from being destroyed by insects and pests.
(e) Some new types of crops are also developed and are being developed to meet the requirement of society.

Question 25.
What is a scientific temperament and scientific way of doing things?
Answer:
A mindset molded in a particular set of thinking called the scientific way is known as scientific temperament. It is not only based on logic, facts but on reliable observations. The ultimate test of truth in science is experimental verification.

A scientific way of doing things involves the following steps:
(a) Identifying the problem or aim.
(b) Collecting all relevant information or data related to the problem.
(c) Hypothesising or proposing a possible theory.
(d) Taking experimental observation yielding consistent results.
(e) Predicting or making statements.

Question 26.
What is the scope of Physics?
Answer:
The scope of Physics is very wide i.e. the domain of Physics covers a very wide variety of natural phenomena.

For example, the range of distances we study in Physics varies from 1014 m (size of the nucleus) to 1025 m (size of the universe).

Similarly, the range of masses included in the study of Physics varies from 10-30 kg (mass of an electron) to 1055 kg (mass of the universe). Also, the range of time i.e. time intervals of events we come across in the study of Physics varies from 1022 seconds (time taken by light to cross a nuclear distance) to 10-8 seconds (lifetime of the sun).

Thus we see that the scope of Physics is really very wide. It includes; optics, electricity waves, and oscillations, heat and thermodynamics, magnetism, atomic and nuclear physics, computers, and electronics.

Question 27.
Physics is an exciting subject! Comment.
Answer:
The study of Physics is exciting in many ways, e g.:

  1. Journey to the moon with controls from the grounds.
  2. Lasers and their ever-increasing applications.
  3. Live transmission of events thousands of kilometers away on the T: V.
  4. The speed and memory of the fifth generation of computers.
  5. Study of various types of forces in nature.
  6. Technological advances in health science.
  7. The use of robots is quite exciting.
  8. Telephone calls over long distances and so on. Thus, Physics is exciting not only to the scientist but also to a layman, children, women, etc. The musical instruments, toy guns, toy trains, etc. all are constructed using simple principles of physics like collision, potential energy, and vibration, etc. Today the situation is that even our thought process and social values are affected by Physics. Thus, it is quite amazing.

Question 28.
Write a short note on the origin and development of Physics.
Answer:
Physics as a science took roots from the days of Copernicus, i. e., nearly four centuries ago when it was not well understood and it was considered as a part of philosophy, i.e., knowledge. Later on, with the development of knowledge about nature and its various activities, the knowledge was divided into physical and biological sciences.

Some important developments like Newton’s law of gravitation, ideas about light were developed in the 18th century. The 19th century saw some of the great discoveries in Physics and at the end f the century i.e. 1889, the electromagnetic theory was developed, Fouriuatun of Einstein’s and Plank’s ideas were laid down apart from laying the basis for the industrial revolution. Physics progressed very fast in the first quarter of the 20th century.

Atomic structure, the theory of relativity, quantum theory, nuclear physics, basics of laser theory and most of the other developments took place in this period. Then came transistors, semiconductors, television, radar, and few important discoveries during World War II.

Further development in quantum mechanics, thin-film technology, computers, lasers was developed from 1950 onward. Today we have no theoretical development beyond quantum mechanics. A unified theory is not being tried yet. This is the present status with achievements in applied fields.

Question 29.
Explain the role of science in the entertainment industry.
Answer:
Progress in science especially in physics and technology has enriched no other field as the field of entertainment. We see scientific toys like robots for children and merry-go-rounds of all sorts in amusement and entertainment parks which are not only highly entertaining but also test the endurance of an individual.

These are based on the laws of forces and the critical stages are those when a man is pitted against gravity. T.V. has invaded a large number of houses as a source of entertainment and so are the music blaring CD players. Computers have become another source of individual indoor entertainment. The use of laser beams in music and drama shows and disco dances is highly rewarding.

With the improvement in physics and technology, circus entertainment to have changed with the application of science. Thus, we conclude that the role of science and technology in the entertainment industry has increased tremendously.

Question 30.
Give some of the uses and applications of artificial satellites.
Answer:
The following are the fields where satellites are being used –
(a) Remote sensing
(b) Communication
(c) Spying
(d) Weather forecasting

(a) Remote sensing: In remote sensing, infrared photography s used from a high altitude. The technique has improved a lot and the resolution has gone down to about 5m in an area. This technique has helped in mineral and oil exploration. It has also helped in the study of forest living and crop patterns.

(b) Communication: In the field of communication, satellites have brought revolution during the last 20 years. Now new items are flashed all around the globe. Cricket matches can be seen anywhere on the globe which is played in one small part of a country. Internet, E-mail, etc. have brought people much more closer and the world has become a unified entity.

(c) Spying: In spying also use IR technology.

(d) Weather forecasting: Weather forecasting has become more reliable with the use of satellites. The rains, cyclones can now be predicted with greater accuracy 36 hours in advance or even earlier. The movement of glaciers, the position of ice and snow deposition, and the resulting flow of water in rivers is known well in advance.

Physical World Important Extra Questions Long Answer Type

Question 1.
How Physics is related to other sciences?
Answer:
Physics is so important to a branch of science that without the knowledge of Physics, other branches of science cannot make any progress.

This can be seen from the following:
(a) Physics in relation to Mathematics: The theories and concepts of Physics lead to the development of various mathematical tools like differential equations, equations of motion, etc.

(b) Physics in n .ation to Chemistry: The concept of iñteraction between various particles leads to understanding the bonding and the chemical structure of a substance. The concept of X-ray diffraction and radioactivity has helped to distinguish between the various solids and to modify the periodic table.

(c) Physics in relation to Biology: The concept of pressure and its measurement has helped us to know the blood pressure of a human being, which in turn is helpful to know the working of the heart. The discovery of X-rays has made it possible to diagnose the various diseases in the body and fracture in bones.

The optical and electron microscopes are helpful in the studies of various organisms. Skin diseases and cancer can be cured with the help of high-energy radiation like x-rays, ultraviolet rays.

(d) Physics in relation to Geology: The internal structure of various rocks can be known with the study of the crystal structure. The age of rocks and fossils can be known easily with the help of radioactivity i.e. with the help of carbon dating.

(e) Physics in relation to Astronomy: Optical telescope has made it possible to study the motion of various planets and satellites in our solar system.

The radio telescope has helped to study the structure of our galaxy and to discover pulsars and quasars (heavenly bodies having star-like structures). Pulsars are rapidly rotating neutron stars. Doppler’s effect predicted the expansion of the universe. Kepler’s laws are responsible to understand the nature of the orbits of the planets around the sun.

(f) Physics in the relation to Meteorology: The variation of pressure with temperature leads to the forecast of the weather.

(g) Physics in relation to Seismology: The movement of the earth’s crust and the types of waves produced help us in studying the earthquake and its effect.

Question 2.
Write a short note on origin and Fundamental forces in nature.
Answer:
These are the following four basic forces in nature:
(a) Gravitational forces
(b) Electromagnetic forces
(c) Weak forces
(d) Strong force or nuclear forces.

Some of the important features of these forces are discussed below:
(a) Gravitational forces: These are the forces of attraction between any two bodies in the universe due to their masses separated by a definite distance. These are governed by Newton’s law of gravitation given by
F = G \(\frac{m_{1} m_{2}}{r^{2}}\)

Class 11 Physics Important Questions Chapter 1 Physical World 1
where m1, m2 are the masses of two bodies
r = distance between them
G = universal gravitational constant
= 6.67 × 10-11 Nm2kg-2

Characteristics of gravitational forces:

  1. They are always attractive. They are never repulsive. They exist between macroscopic as well as microscopic bodies.
  2. They are the weakest forces in nature.
  3. They are central forces in nature i.e. they set along the line joining the centers of two bodies.
  4. They are conservative forces.
  5. They obey inverse square law i.e. F ∝\(\frac{1}{r^{2}}\) they vary inversely as the square of the distance between the two bodies.
  6. They are long-range forces i.e. gravitational forces between any two bodies exist even when their distance of separation is quite large.
  7. The field particles of gravitational forces are called gravitons. The concept of the exchange of field particles between two bodies explains how the two bodies interact from a distance.

(b) Electromagnetic forces: They include the electrostatic and magnetic forces. The electrostatic forces are the forces between two static charges while magnetic forces are the forces between two magnetic poles. The moving charges give rise to the magnetic force. The combined action of these forces is called electromagnetic forces.

Characteristics of electromagnetic forces:

  1. These forces are both attractive as well as repulsive.
  2. They are central forces in nature.
  3. They obey inverse square law.
  4. They are conservative forces in nature.
  5. These forces are due to the exchange of particles known as photons which carry no charge and have zero rest mass.
  6. They are 1036 times stronger as compared to gravitational forces and 1011 times stronger than weak forces.

(c) Strong forces: They are the forces of nuclear origin. The particles inside the nucleus are charged particles (protons) and neutral particles (neutrons) which are bonded to each other by a strong interaction called nuclear force or strong force. Hence they may be defined as the forces binding the nucleons (protons and neutrons) together in a nucleus. They are responsible for the stability of the atomic nucleus.

They are of three types:

  1. n-n forces are the forces of attraction between two neutrons.
  2. p-p forces are the forces of attraction between two protons.
  3. n-p forces are the forces of attraction between a proton and a neutron.

Characteristics of Nuclear forces:

  1. They are basically attractive in nature and become repulsive when the distance between nucleons is less than O.S fermi.
  2. They obey inverse square law.
    (a) and
    (b) types are the forces that we encounter in the macroscopic world while
    (c) and
    (d) types are the forces that we encountered in the microscopic world.

(c) Weak forces: They are defined as the interactions which take, place between elementary particles during radioactive decay of a radioactive substance. In P-decay, the nucleus changes into a proton, an electron, and a particle called anti-neutrino (which is uncharged). The interaction between the electron and the anti-neutrino is known as weak interaction or weak force.

Characteristics of Weak forces:

  • They are 1025 times stronger than the gravitational forces.
  • They exist between leptons and leptons, leptons and mesons. etc.

Question 3.
Distinguish between the studies in the fields of science, engineering, and technology. Give an outline of the two or three industrial revolutions brought about by advancements in technology over the last twenty-five years or so.
Answer:
Science is concerned with the unfolding of the basic aspects of nature. It formulates simple laws and finds the rhythm in nature, materials, and energy. Using basic principles of science, the ways to use them for the production of different kinds of articles is called technology, i.e., it is the application of science.

The execution of the application of technology in engineering. The production of articles using machines and implements in engineering. This involves the design, development, and manufacturing of articles.

The most notable technology development in the last 25 years is in the field of information technology, computers, and electronic media. The revolution in information technology has opened up fields on the internet, satellite linking of information systems and services other peripheral developments in the industry.

Computers have changed the face of society and made life easy in several fields. It has improved work efficiency in many segments of the industry and public life. Computers have touched the lives of children playing video games and adults alike. It has helped big organizations like railways, banks, and financial institutions like the insurance sector.

India has become one of the biggest centers of software exports and a big foreign exchange earner. Advance scientific research and industrial designing are being done by computers. TV has entered most Indian houses and community centers-courtesy revolution in electronic media.

The younger generation is mad after the stereo music with CD facilities. The transistors and tape recorders are left far behind. Electronic media has changed the face of the entertainment industry as well as information dissemination. Quick transmission of news, views, and comments are accepted as natural ones by listeners and viewers.

Value-Based Type:

Question 1.
A debate was organized by a school on woman’s innate nature, capacity, and intelligence. The arguments given by the two groups were as under:
Team A: Nature makes little difference in men and women in their anatomy and feeling. So, women are not on par with men. Hence, she is inferior to men in spheres of activity like sports, scaling of mountains like the Himalayas, etc.
Team B: The students of team ‘B’ have demolished this view using scientific arguments, and by quoting examples of great women, in science and other spheres; and persuade yourself and others that, give equal opportunity, women are on par with men.
Now, Answer these questions:
(i) Which values are displayed by team ‘B’?
Answer:
The values displayed by team B are:
(a) Gender equality.
(b) Justice and support to women.
(c) Equal opportunities to women.

(ii) Do you think team B was correct? Give proper justification with examples.
Answer:
Yes, there is no difference in the capacity of women and men as far as working capacity, intelligence, decision making is concerned. It is a biological fact that the development of the human brain does not depend upon sex but on nutrition contents and heredity. If equal opportunities are afforded to both men and women, then the female mind will be as efficient as the male mind.

The list of successful women from various fields is as under Kalpana Chawala, Madame Curie, Indira Gandhi, Mother Teresa, Margaret Thatcher, etc.

Question 2.
Two friends of class XI Mohan and Raghav were discussing the role of physics in society. Mohan Said to Raghav that physics does not have any impact on our society. Since he was a student of Arts Stream. But Mohan who is a science student explained that physics and Society are directly linked because whatever is discovered in physics, it immediately affects society.

The latest technology has played an important role in the fields of communication such as radios, computers, TVs, mobile phones and connects the people with each other. Nuclear energy has brought a profound change in the thinking and living style of human beings.
(i) Which values are displayed here by Mohan?
Answer:
The values displayed by Mohan are :
(a) Intelligence
(b) Awareness
(c) Logical

(ii) Give some discoveries which have really affected society more.
Answer:
(a) Theory of relativity
(b) X-ray
(c) Radioactivity
(d) Photoelectric effect
(e) Steam engine (based on laws of thermodynamics)
(f) Computer (Based on Digital logic)
(g) Super Conductivity
(h) Radio and TVs.

Question 3.
India has had a long and unbroken tradition of great Scholarship in mathematic, astronomy, linguistics, logic, and ethics. Yet, in parallel with this, several superstitious and obscurantist attitudes and practices flourished in our society and unfortunately continue even today-among many educated people too.

A student of Class XI gave an idea to overcome this evil of our society by using scientific explanations through mass media, radio television, and newspapers.
(i) Which values are displayed by the student?
Answer:
(a) Awareness
(b) Scientific and logical ideas
(c) Concern for the upliftment of our society to eradicate the evils of society.
(d) Intelligence, Sharp mind.

(ii) How will you use your knowledge of science to develop strategies to counter these attitudes?
Solution:
Educating the common man is the only way to get rid of superstitions and obscurantist attitudes. The mass media like newspapers, magazines, radio, television, etc. Can play a vital role. School and college curriculum can be suitably developed so that there is an emphasis on these topics. Teachers can play an important role to organize the seminar and motivate them.

Question 4.
A seminar was organized to know the views of students on whether the particular application is good, bad or something that cannot be so clearly categorized:
(a) Prenatal sex determination.
(b) Development of nuclear weapons.
(c) Mass vaccination
(d) Cloning
(e) Purification of water for drinking.

Now, answers these questions:
(i) Which values arc depicted here?
Answer:
To create awareness through group activities, to develop problem-solving ability, scientific knowledge can be put to good or bad use, depending on the user.

(ii) Do you think such type of group activities are important in day-to-day life?
Answer:
Yes.

(iii) Give justification for each of the above topics from (a-e):
Answer:
(a) Bad, it leads to the practice of abortion in the case of the female fetus.
(b) Bad, because nuclear weapons may cause mass destruc¬tion of mankind.
(c) Good, because it helped to eradicate the disease.
(d) Bad, because it can destroy the normal family life.
(e) Good, because it will help to improve good health of the citizens.

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