Category: CBSE Class 10

NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4 are part of NCERT Solutions for Class 10 Maths. Here we have given NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4.

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Maths
Chapter	Chapter 8
Chapter Name	Introduction to Trigonometry
Exercise	Ex 8.4
Number of Questions Solved	5
Category	NCERT Solutions

NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4

Question 1.
Express the trigonometric ratios sin A, sec A and tan A in terms of cot A.
Solution:
From trigonometric identity, cosec² A – cot² A = 1, we get

Question 2.
Write all the other trigonometric ratios of ∠A in terms of sec A.
Solution:
Since sin² A + cos² A = 1, therefore

Question 3.
Evaluate:
(i)

(ii) sin 25° cos 65° + cos 25° sin 65°
Solution:

(ii) sin 25° cos 65° + cos 25° sin 65° = sin 25° cos (90° – 25°) + cos 25° sin (90° – 25°)
= sin 25° sin 25° + cos 25° cos 25°
= sin² 25° + cos² 25° = 1

Question 4.
Choose the correct option. Justify your choice.
(i) 9 sec² A – 9 tan² A =
(A) 1
(B) 9
(C) 8
(D) 0

(ii) (1 + tan θ + sec θ) (1 + cot θ – cosec θ ) =
(A) 0
(B) 1
(C) 2
(D) -1

(iii) (sec A + tan A) (1 – sin A) =
(A) sec A
(B) sin A
(C) cosec A
(D) cos A

(iv) \(\frac{1+\tan ^{2} A}{1+\cot ^{2} A}\)
(A) sec² A
(B) -1
(C) cot² A
(D) tan² A
Solution:
(i) 9 sec² A – 9 tan² A = 9(sec² A – tan² A) = 9 x 1 = 9
Correct option is (B)

Question 5.
Prove the following identities, where the angles involved are acute angles for which the expressions are defined.

Solution:

We hope the NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4, help you. If you have any query regarding NCERT Solutions for Class 10 Maths Chapter 8 Introduction to Trigonometry Ex 8.4, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 10 Maths Chapter 12 Areas Related to Circles Ex 12.2 are part of NCERT Solutions for Class 10 Maths. Here we have given NCERT Solutions for Class 10 Maths Chapter 12 Areas Related to Circles Ex 12.2.

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Maths
Chapter	Chapter 12
Chapter Name	Areas Related to Circles
Exercise	Ex 12.2
Number of Questions Solved	14
Category	NCERT Solutions

NCERT Solutions for Class 10 Maths Chapter 12 Areas Related to Circles Ex 12.2

Question 1.
Find the area of a sector of a circle with radius 6 cm if angle of the sector is 60°.
Solution:
Radius of the sector (r) = 6 cm
Central angle of the sector = 60°

Question 2.
Find the area of a quadrant of a circle whose circumference is 22 cm.
Solution:
Let radius of the circle = r
∴ Circumference of the circle = 2πr

Question 3.
The length of the minute hand of a clock is 14 cm. Find the area swept by the minute hand in 5 minutes.
Solution:
Length of minute hand of the clock = 14 cm

Question 4.
A chord of a circle of radius 10 cm subtends a right angle at the centre. Find the area of the corresponding:
(i) minor segment
(ii) major segment (Use ? = 3.14)
Solution:
Given: radius of the circle = 10 cm
Angle subtended by chord at centre = 90°
(i) Area of the minor segment

(ii) Area of the major segment = Area of the circle – Area of the minor segment
= πr² – 28.5 = 3.14 x 10 x 10-28.5
= 314-28.5 = 285.5 cm²

Question 5.
In a circle of radius 21 cm, an arc subtends an angle of 60° at the centre. Find:
(i) length of the arc.
(ii) area of the sector formed by the arc.
(iii) area of the segment formed by the corresponding chord.
Solution:
Radius of the circle = 21 cm
Angle at the centre = 60°

Question 6.
A chord of a circle of radius 15 cm subtends an angle of 60° at the centre. Find the areas of the corresponding minor and major segments of the circle. (Use π = 3.14 and \(\sqrt{3}\) = 1.73)
Solution:
Radius of the circle = 15 cm
Angle subtended by chord at centre = 60°
Area of the sector = \(\frac{\pi r^{2} \theta}{360^{\circ}}\) = 3.14 x \(\frac{15 \times 15 \times 60^{\circ}}{360^{\circ}}\) = 117.75 cm²
Area of the triangle formed by radii and chord = \(\frac { 1 }{ 2 }\)r²θ
= \(\frac { 1 }{ 2 }\)(15)² sin 60° = \(\frac { 1 }{ 2 }\) x 15 x 15 x \(\frac{\sqrt{3}}{2}\) = 97.31 cm²
Area of the minor segment = Area of the sector – Area of the triangle formed by radii and chord
= 117.75 – 97.31 = 20.44 cm²
Area of the circle = πr² = 3.14 x 15 x 15 = 706.5 cm²
Area of the circle – Area of the minor segment
= 706.5 – 20.44 = 686.06 cm²

Question 7.
A chord of a circle of the radius 12 cm subtends an angle of 120° at the centre. Find the area of the corresponding segment of the circle. (Use π = 3.14 and \(\sqrt{3}\) = 1.73).
Solution:
Radius of the circle = 12 cm
Angle subtended by chord at centre = 120°

Area of the corresponding segment = Area of the sector – Area of A formed by radii and chord
= 150.72 – 62.28 cm² = 88.44 cm²

Question 8.
A horse is tied to a peg at one corner of a square shaped grass field of side 15 m by means of a 5 m long rope (see figure). Find

(i) the area of that part of the field in which the horse can graze.
(ii) the increase in the grazing area if the rope were 10 m long instead of 5 m. (Use n = 3.14)
Solution:
(i) Length of the rope = Radius of the sector grazed by horse = 5 m
Here, angle of the sector = 90°

Length of the rope is increased from 5 m to 10 m
New radius of sector grazed by horse = 10 m

Question 9.
A brooch is made with silver wire in the form of a circle with diameter 35 mm. The wire is also used in making 5 diameters which divide the circle into 10 equal sectors as shown in figure.

Find:
(i) the total length of the silver wire required.
(ii) the area of each sector of the brooch.
Solution:
Length of one diameter = 35 mm
Total length of 5 diameters = 5 x 35 mm = 175 mm
Circumference of the circle = 2π = 2 x \(\frac { 22 }{ 7 }\) x \(\frac { 35 }{ 2 }\) = 110 mm
(i) Total length of the wire used = length of 5 diameters + circumference of brooch
= 175 + 110 = 285 mm

(ii) Total sectors are 10.

Question 10.
An umbrella has 8 ribs which are equally spaced (see figure). Assuming umbrella to be a flat circle of radius 45 cm, find the area between the two consecutive ribs of the umbrella.

Solution:
Radius of the circle = 45 cm
Number of ribs = 8

Question 11.
A car has two wipers which do not overlap.
Each wiper has a blade of length 25 cm sweeping through an angle of 115°. Find the total area cleaned at each sweep of the blades.
Solution:
Given: length of blade of wiper = radius of sector sweep by blade = 25 cm
Area cleaned by each sweep of the blade = area of sector sweep by blade
Angle of the sector formed by blade of wiper =115°

Question 12.
To warn ships for underwater rocks, a lighthouse spreads a red coloured light over a sector of angle 80° to a distance of 16.5 km. Find the area of the sea over which the ships are warned. (Use π = 3.14)
Solution:
Angle of the sector = 80°
Distance covered = 16.5 km
Radius of the sector formed = 16.5 km

Question 13.
A round table cover has six equal designs as shown in the figure. If the radius of the cover is 28 cm, find the cost of making the designs at the rate of ₹ 0.35 per cm². (Use \(\sqrt{3}\) = 1.7)

Solution:
Radius of the cover = 28 cm
∵ There are six equal designs

Question 14.
Tick the correct answer in the following: Area of a sector of angle p (in degrees) of a circle with radius R is
(a) \(\frac{p}{180^{\circ}}\) × 2πR
(b) \(\frac{p}{180^{\circ}}\) × πR²
(c) \(\frac{p}{360^{\circ}}\) × 2πR
(d) \(\frac{p}{720^{\circ}}\) × 2πR²
Solution:
Sector angle isp in degrees
Radius of the circle = R
Area of the sector = \(\frac{\pi \mathrm{R}^{2} p}{361^{6}}\) = \(\frac{\left(\pi R^{2} p\right) 2}{720^{\circ}}\)
= \(\frac{p}{720^{\circ}}\) × 2πR²

We hope the NCERT Solutions for Class 10 Maths Chapter 12 Areas Related to Circles Ex 12.2, help you. If you have any query regarding NCERT Solutions for Class 10 Maths Chapter 12 Areas Related to Circles Ex 12.2, drop a comment below and we will get back to you at the earliest.

On this page, you will find NCERT Class 10 Economics Chapter 5 Notes Pdf free download. CBSE Class 10 Social Science Notes Economics Chapter 5 SST Consumer Rights will seemingly, help them to revise the important concepts in less time.

Consumer Rights Class 10 Notes Social Science Economics Chapter 5

CBSE Class 10 Economics Chapter 5 Notes Understanding the Lesson

1. People participate in the market both as producers and consumers. As producers of goods and services they could be working in any of the sectors. As consumers they participate in the market when they purchase goods and services that they need.

2. Rules and regulations are required for the protection of the consumers in the market place because markets do not work in a fair manner. Producers are few and powerful whereas consumers purchase in small amounts and are scattered. At times false information is passed on through the media, and other sources to attract consumers.

3. The consumer movement arose out of dissatisfaction of the consumers as many unfair practices were being indulged in by the sellers. There was no legal system available to consumers to protect them from exploitation in the market place.

4. In India, consumer movement originated slowly and steadily. Till the 1970s, consumer organizations were largely engaged in writing articles and holding exhibitions. They formed consumer groups to look into the malpractices in ration shops. Gradually, the number of consumer groups increased in the country.

5. The movement got success in creating pressure on business firms as well as government to correct business conduct. In 1986, the Indian government enacted the Consumer Protection Act, popularly known as COPRA.

6. As consumers, we have the right to be protected against the marketing of goods and delivery of services that are hazardous to life and property. Producers need to strictly follow the required safety rules and regulations because safety is everyone’s right.

7. Consumers have the right to be informed about the particulars of goods and services that they purchase. They can then complain and ask for compensation or replacement if the product proves to be defective in any manner.

8. In recent times, the consumers’ right to information has been expanded to cover various services provided by the Government. In October 2005, the Government of India enacted a law, known as Right to Information Act. The law ensures its citizens all the information about the functions of government departments.

9. Consumers have the right to choose whether to continue to receive the service. Consumers have also the right to seek redressal against unfair trade practices and exploitation. If any damage is done to a consumer, he/she has the right to get compensation depending on the degree of damage.

10. Consumer Forums or Consumer Protection Council guide consumers on how to file cases in the consumer court. On many occasions, they also represent individual consumers in the consumer courts.

11. Under COPRA, three-tier quasi-judicial machinery at the district, state and national levels was set up for redressal of consumer disputes. If a case is dismissed in district level court, the consumer can also appeal in state and then in national-level courts.

12. The Consumer Protection Act or COPRA has enabled consumers to have the right to represent in the consumer courts. The enactment of this Act has led to the setting up of separate departments of Consumer Affairs in central and state governments.

13. India has been observing 24 December as the National Consumer’s Day. India is one of the countries that have exclusive courts for consumer redressal.

14. The consumer redressal process is becoming difficult, expensive and time-consuming. The existing laws also are not very clear on the issue of compensation to consumers injured by defective products.

15. After more than 25 years of the enactment of COPRA, consumer awareness in India is spreading but slowly. It is rightly said that consumer movements can be effective only with the consumers’ active involvement.

Consumer Rights Class 10 CBSE Notes Important Terms

Consumer: A person who buys things or uses services.

Adulterated: Impure.

Producer: A person, company or country that makes or grows something.

Rampant: Existing or spreading everywhere in a way that is very difficult to control.

Compensation: Money that you pay to somebody because you have injured him/her or lost or damaged his/her property.

Redressal: Compensation for injuries sustained.

Cumbersome: Large or heavy and therefore, difficult to carry or use.

Enactment: The process of passing legislation.

On this page, you will find NCERT Class 10 Civics Chapter 8 Notes Pdf free download. CBSE Class 10 Social Science Notes Civics Chapter 8 SST Challenges to Democracy will seemingly, help them to revise the important concepts in less time.

Challenges to Democracy Class 10 Notes Social Science Civics Chapter 8

CBSE Class 10 Civics Chapter 8 Notes Understanding the Lesson

1. Democracy is a dominant form of government in the contemporary world. But the promise of democracy is far from realised anywhere in the world.

2. Although democracy does not have a challenger, that does not mean that it does not face any challenges. Different countries face different kinds of challenges.

3. The countries not under democratic government face the foundational challenge of making the transition to democracy and then instituting democratic government.

4. Most of the established democracies face the challenge of expansion. This involves applying the basic principle of democratic government across all the regions, different social groups and various institutions.

5. The third challenge of deepening of democracy is faced by every democracy in one form or another. This involves strengthening of the institutions and practics of democracy.

6. Each of the above challenges is linked to the possibility of reforms. Since all the countries do not have the same challenges, so they cannot follow the same recipe of political reforms.

7. When we talk in the context of our country, we can develop some proposals for reforms at the national level. But the real challenge of reforms may not lie at the national level. Some of the crucial questions need to be thought at the state or local level.

8. While devising ways and means for political reforms in India, some broad guidelines should be kept in mind; for example, legal ways of reforming politics. Carefully devised changes in law can help to discourage wrong political practices and encourage good ones. But legal constitutional changes by themselves cannot overcome challenges to democracy. In fact, democratic reforms are to be carried out mainly by political activists, parties, movements and politically conscious citizens.

9. Those laws are good which empower people to carry out democratic reforms. The Right to Information Act empowers the people to find out what is happening in government and act as watchdogs of democracy.

10. Democratic reforms are to be brought about principally through political practice. Therefore, the main focus of political reforms should be on ways to strengthen democratic practice.

11. Any proposal for political reforms should think not only about what is a good solution but also about who will implement it and how.

Challenges to Democracy Class 10 CBSE Notes Important Terms

Challenge: A difficulty that carries within it an opportunity for progress.

Foundational: Denoting an underlying basis or principle.

Guideline: A general rule, principle, or piece of advice.

Watchdog: A person or group of persons that acts as a protector or guardian against inefficiency, illegal practices, etc.

Reform: The action or process of reforming an institution or practice.

On this page, you will find NCERT Class 10 Civics Chapter 5 Notes Pdf free download. CBSE Class 10 Social Science Notes Civics Chapter 5 SST Popular Struggles and Movements will seemingly, help them to revise the important concepts in less time.

Popular Struggles and Movements Class 10 Notes Social Science Civics Chapter 5

CBSE Class 10 Civics Chapter 5 Notes Understanding the Lesson

1. Power-sharing is important in a democracy and different tiers of government and various social groups share power. Those who exercise power are constrained by the influence and pressure exerted on them.

2. Democracy involves conflict of interests and viewpoints. These differences are often expressed in organized ways. Those who are in power are required to balance these conflicting demands and pressures.

3. Struggles around conflicting demands and pressures shape democracy. Various pressure groups and movements influence politics using indirect ways.

4. The popular struggles in Nepal and Bolivia are two examples in this regard which were made successful with the help of organizations like Seven Party Alliance (SPA) and FEDECOR respectively.

5. The movement in Nepal was to establish democracy while the struggle in Bolivia involved claims on an elected, democratic government. Both these struggles were successful but their impact was at different levels.

6. There are many indirect ways in which people can get governments to listen to their demands or their points of view. They could do so by forming an organization and undertaking activities to promote their interests or their viewpoints. These are called interest groups or pressure groups.

7. Pressure groups influence government policies. They do not aim to directly control or share political power.

8. Movements too attempt to influence politics rather than directly take part in electoral competition; for example, Narmada Bachao Andolan, Movement for Right to Information, etc.

9. Interest groups seek to promote the interests of a particular section or group of society; for example, Trade Unions, Business Associations, etc. Their chief concern is the betterment and well-being of their members, not society in general.

10. Narmade Bachao Andolan is a good example of a single-issue movement. It can be contrasted with movements like environmental movement and women’s movement that are long term and involve more than one issue.

11. Pressure groups and movements exert influence on politics in a variety of ways-by carrying out information campaigns, organizing meetings, filing petitions, etc. They also organise protest activity like strikes or disrupting government programmes.

Note: Please note as per the CBSE curriculum 2017-18, chapter-5 has to be done as project work only and will not be evaluated in theory.

Popular Struggles and Movements Class 10 CBSE Notes Important Terms

Maoists: Those communists who believe in the ideology of Mao, the leader of the Chinese Revolution. They seek to overthrow the government through an armed revolution so as to establish the rule of the peasants and workers.

Ultimatum: A final demand, with a threat of hostile action if this is rejected.

Mobilisation: Act of marshalling and organising and making ready for use or action.

Pressure group: A group of people having common interests which exert pressure on the government for fulfilment of their interests.

Movement: A loose organisation which depends on spontaneous mass participation.

On this page, you will find NCERT Class 10 Civics Chapter 3 Notes Pdf free download. CBSE Class 10 Social Science Notes Civics Chapter 3 SST Democracy and Diversity will seemingly, help them to revise the important concepts in less time.

Democracy and Diversity Class 10 Notes Social Science Civics Chapter 3

CBSE Class 10 Civics Chapter 3 Notes Understanding the Lesson

1. Language and region are not the only features that give a distinct identity to people. Sometimes, people also identify themselves on the basis of their physical appearance, class, religion, gender, caste, tribe, etc.

2. In 1968 Olympics held at Mexico City, Tommie Smith and John Carlos, both African-Americans, won the gold and bronze medals respectively in 200 metres race. In the medal ceremony they received their medals wearing black socks and no shoes to represent black poverty. They did so because they wanted to draw international attention to racial discrimination in the United States.

3. The International Olympic Association held Carlos and Smith guilty of violating the Olympic spirit by making a political statement. Their medals were taken back. But their action gained international attention for the Civil Rights Movement in the US.

4. The athletes in the above example responded to social divisions and social inequalities which exist in almost all societies. Social diversity can take different forms in different societies.

5. Some social differences are based on accident of birth and some are based on our choices. But every social difference does not lead to social division. Social differences divide similar people from one another but they also unite very different people.

6. People belonging to different social groups share differences and similarities cutting across the boundaries of their groups. We all have more than one identity and can belong to more than one social group.

7. Social division takes place when some social difference overlaps with other differences. The difference between the Blacks and Whites becomes a social division in the US because Blacks are poor and discriminated against. In our country Dalits face discrimination and injustice. Situation of this kind produces social divisions.

8. If social differences cross cut one another, it is difficult to pit one group of people against the other. It means that groups that share a common interest on one issue are likely to be in different sides on a different issue.

9. Overlapping social differences create possibilities of deep social divisions and tensions. Cross-cutting social differences are easier to accommodate. Social divisions of one kind or another exist in most countries. It does not matter whether the country is small or big.

10. The combination of politics and social divisions is very dangerous. The competition among various political parties tends to divide any society. If they start competing in terms of some existing social divisions, it can make social divisions into political divisions and lead to conflict and tension in the country. So politics and social divisions must not be allowed to mix.

11. But every expression of social divisions in politics does not lead to disasters. Social divisions of one kind or another exist in most countries of the world. Wherever they exist, these divisions are reflected in politics.

18. Social divisions affect voting in most countries. People from one community tend to prefer some party more than others. But this does not lead to disintegration of the country.

19. Three factors that determine the outcomes of politics of social divisions are- how people perceive their identities, how political leaders raise the demands of any community and how the government reacts to demands of different groups.

20. The assertion of social diversities in a country need not be seen as a source of danger. In a democracy, political expression of social divisions can be healthy. This allows various disadvantaged and marginal social groups to express their grievances and get the government to attend to these.

21. But these people need to fight against the injustices. Such a fight often takes the democratic path, voicing their demands in a peaceful and constitutional manner and seeking a fair position through elections. Sometimes the struggle against inequalities takes the path of violence. However, democracy is the best way to fight for recognition.

Democracy and Diversity Class 10 CBSE Notes Important Terms

African-American: Descendants of Africans who were brought into America as slaves between the 17th century and early 19th century.

Homogeneous society: A society that has similar kinds of people, especially where there are no significant ethnic differences.

Migrant: Anybody who shifts from one region or country to another region within a country or to another country, usually for work or other economic opportunities.

Outcome: The result of an event.

Racism: A belief in the superiority of a particular race.

On this page, you will find Management of Natural Resources Class 10 Notes Science Chapter 16 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 16 Carbon and its Compounds will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 16 Notes Management of Natural Resources

Management of Natural Resources Class 10 Notes Understanding the Lesson

1. Natural resources: The resources provided by the nature and utilised by human beings are called natural resources. Example: Soil, air, water, forests, wildlife, coal, petroleum, etc. Management of Natural Resources is necessary for their conservation and sustainable development.

2. Efforts for Environment Protection: There are international laws and regulations; National laws and acts creating awareness and National and international organisations working towards protecting our environment.

3. Ganga Action Plan: A multi-crore project came about in 1985 to improve quality of the water in the Ganga.

4. Coliform: A group of bacteria found in human intestines. Its presence in water indicates contamination by disease-causing microorganisms.

5. Survey for Coliform Count in 1993-1994: The results of survey done in 1993-1994 for finding total coliform in terms of MPN/100 mL is:
Minimum desired level 450 MPN/100 mL; Minimum level found in Rishikesh 600-650 MPN/100 mL; Maximum level found in Kannauj 1400 MPN/100 mL.

6. Pollution of the Ganga: The Ganga runs a course of 2500 km from Gangotri in the Himalayas to Ganga Sagar in the Bay of Bengal. It is getting polluted due to the flow of garbage, excreta, untreated sewage which are dumped into it. Also, human activities like bathing, washing of clothes and immersion of ashes or unbumt corpses, chemical effluents from industries increase its pollution load. This leads to toxicity which kills fish in large sections of the river.

7. The three R’s to save the environment: Reduce, Recycle and Reuse.

8. Reduce: Use less and not to waste any resource.

9. Recycle: Segregate the waste that can be recycled and make required things by using them,

10. Reuse: Use the things again and again.

11. Reuse is better than recycling: Reusing helps to save energy, so it is better than recycling.

12. Concept of sustainable development: Encourage forms of growth and development which helps to meet current basic human needs while preserving the resources for the needs of future generations. In this way economic development is linked to environmental conservation.

13. Need to Manage Natural Resources: The human population is increasing at a tremendous rate due to improvement in health care, so the demand for all resources is increasing at an exponential rate. Since the resources are limited, the management of natural resources is necessary, so that these will last for the generations to come. This management would help in equitable distribution of resources and reducing the damage being done to the environment.

14. Biodiversity Hot Spots: Forests are biodiversity hot spots. Number of species found in an area is one of the measures of biodiversity along with the range of different life forms (bacteria, fungi, ferns, flowering plants, nematodes, insects, birds, reptiles, etc.)

15. Result of loss in biodiversity: Experiments and field studies suggest that a loss of diversity may lead to a loss of ecological stability.

16. Stakeholder: A person having interest or concern for something is called as stakeholder. The various stakeholders for the conservation of forests are:

• Local People: Those who are dependent on forests for their survival.
• Forest Department: Government who owns the land and controls resources
• Industrialists: Those who use various forests
• Wildlife enthusiasts: Those who want to conserve nature

17. Efforts of Bishnoi community in Rajasthan: Bishnoi community of Rajasthan has religiously being protecting the environment. ‘Amrita Devi Bishnoi National Award for Wildlife Conservation’ is given by the Government in the memory of Amrita Devi Bishnoi, who in 1731 AD sacrificed her life along with 363 others for the protection of‘khejri’ trees in Khejarli village near Jodhpur in Rajasthan.

18. Sustainable Management: The management of forest resources wisely and judiciously to fulfil needs of present generation as well as future generations.

19. The Chipko Andolan (‘Hug the Trees Movement’): This movement for conservation of forests originated in a remote village called Reni in Garhwal Himalayas during the early 1970s when the women of the village clasped the tree trunks thus preventing the workers of logging contractor from felling the trees.

20. People’s Participation in the Management of Forests: In 1972, the West Bengal Forest Department failed in reviving the degraded Sal forests in the south-western districts of the state by methods of surveillance and policing. Complete alienation of the people from the administration led to movements by the Naxalites and into frequent clashes between forest officials.

21. Due to efforts of forest officer A.K. Baneijee, villagers were involved in the protection of 1,272 hectares of badly degraded Sal forest. Villagers were given employment in both silviculture and harvesting operations, 25 per cent of the final harvest, and allowed fuel wood and fodder collection on payment of a nominal fee in return of such help in protection. By 1983, the previously worthless Sal forests in Arabari forest range of Midnapore district underwent a remarkable recovery and were valued ? 12.5 crores with the active and willing participation of the local community.

22. Water as a Resource
Reasons for failure to sustain water availability underground:
Loss of vegetation cover, diversion for high water demanding crops, and pollution from industrial effluents and urban wastes.

23. Dams
Advantages of Dams:

• Ensure the storage of adequate water for irrigation and generating electricity.
• Canal systems leading from these dams can transfer large amounts of water great distances. Disadvantages of Dams:
• No equitable distribution of water.
• Large number of people displaced without compensation.
• Huge amount of public money is involved without giving proper benefits.
• Loss of biological diversity and deforestation.

24. Criticisms about large dams: They lead to

• Social problems: They displace large number of peasants and tribals without adequate compensation or rehabilitation.
• Economic problems: They swallow up huge amounts of public money without the generation of proportionate benefits.
• Environmental problems: They contribute enormously to deforestation and the loss of biological diversity.

25. Narmada Bachao Andolan (‘Save the Narmada Movement’): The movement started against the raising of the height of the Sardar Sarovar Dam on the river Narmada.

26. Water Harvesting: Watershed management emphasises scientific soil and water conservation in order to increase the biomass production.

27. Aim: To develop primary resources of land and water to produce secondary resources of plants and animals for use in a manner that will not cause ecological imbalance.

28. Benefits of Watershed management:

• Increases the production and income of the watershed community
• Mitigates droughts and floods
• Increases the life of the downstream dam and reservoirs.

29. Various ancient methods of water harvesting:

• Khadins, tanks and nadis in Rajasthan
• Bundhis in Madhya Pradesh and Uttar Pradesh
• Kulhs in Himachal Pradesh
• Eris (tanks) in Tamilnadu
• Kattas in Karnataka
• Bandharas and tals in Maharashtra
• Ahars and pynes in Bihar
• Ponds in the Kandi belt of Jammu region
• Surangams in Kerala,

30. Purpose of Water Harvesting:

• To recharge the ground water beneath.

31. Advantages of water stored in the ground:

• It does not evaporate.
• Spreads out to recharge wells and provides moisture for vegetation over a wide area.
• Does not provide breeding grounds for mosquitoes like stagnant water.
• It is relatively protected from contamination by human and animal waste.

32. Coal and Petroleum

• They are generally called fossil fuels.
• They are formed from the degradation of biomass millions of years ago.
• They will be exhausted in the future no matter how carefully we use them.
• Petroleum resources will last for about forty years while coal resources will last for two hundred years.
• They contain carbon, hydrogen, nitrogen and sulphur.
• They produce carbon dioxide, water, oxides of nitrogen and oxides of sulphur on being burnt.
• Carbon monoxide is formed instead of carbon dioxide, when they are burnt in insufficient amount of oxygen.
• The oxides of sulphur and nitrogen and carbon monoxide are poisonous at high concentrations and carbon dioxide is a greenhouse gas.
• Increase in amount of carbon dioxide is leading to global warming.

33. Ways to use resources judiciously:

• Taking a bus, public transport or walking/cycling instead of a private vehicle.
• Using LED bulbs in homes instead of normal bulbs.
• Taking the stairs instead of lift.
• Wearing an extra sweater on cold days instead of burning fossil fuels for warmth.

Class 10 Science Chapter 16 Notes Important Terms

Natural Resources: The stocks of nature such as air, water, soil, forests and wildlife. Biodiversity: The diversity of life forms present on Earth.

Sustainable Management: The judicious and wise use of natural resources to fulfil needs of present generation and preserving them for needs of the future generations.

Coliform: Group of gram negative, rod shaped bacteria found in polluted water and in human intestine. Coliform Count: Measure of pollution level of a water body on the basis of presence of coliform bacteria.

Silviculture: Practice of growing trees. Helpful in replenishment of forests.

Monoculture: A culture of single type of plant or tree in an area of forest.

Deforestation: Cutting down trees.

Afforestation: Growing or planting trees.

Reforestation: Growing or planting trees in a deforested area which previously had trees and vegetation.

On this page, you will find Our Environment Class 10 Notes Science Chapter 15 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 15 Our Environment will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 15 Notes Our Environment

Our Environment Class 10 Notes Understanding the Lesson

1. Environment: Everything which surrounds us is environment. It may include living (biotic) and non-living (abiotic) components.

2. Biodegradable substances: Substances that can be slowly destroyed and broken down into very small parts by natural processes with the help of bacteria, fungi, etc. Example: Organic wastes like vegetable and fruit peels, dead plants and animals, etc.

3. Non-biodegradable substances: Substances which cannot be broken down or decomposed into the soil by natural agents are called non-biodegradable. Example: Plastics, polystyrene, metals, aluminium cans, toxic chemicals, paints, etc.

4. Problem due to Non-biodegradable substances: The non-biodegradable substances persist in the j environment for a long time as they are usually unreactive (inert) and may be harmful for the members of the ecosystem.

5. Same enzyme does not break-down everything (Reason for pollution by plastic):
Enzymes are highly specific in their action. Due to this specificity of the enzymes to act on a particular substrate only, many human-made materials like plastics are not broken down by the action of enzymes of bacteria or other saprophytes.
These materials are acted upon by physical processes like heat and pressure which makes them persistent for several thousand years.

6. Ecosystem: All the interacting organisms in an area together with non-living components form an ecosystem.

Types of Ecosystem
	Natural Ecosystem	Man-made Ecosystem
Terrestrial [on land]	Forest, Desert, Grassland	Cropland, Garden
Aquatic [in water]	Fresh water: River, Lake, Pond Marine: Sea, Oceans	Aquarium

On the basis of their position or role in the ecosystem, the organisms are classified as:

1. Producers: The organisms which can synthesise their own food by the process of photosynthesis in presence of sunlight, i.e., all green plants, blue green algae, some photosynthetic bacteria, etc.

2. Consumers: Consumers feed on producers or other consumers to survive. They directly or indirectly depend on producers for their food.

Types of Consumers
Herbivores	Carnivores	Omnivores	Parasites
Feed on plant or plant parts. Example: Rabbit, . Goat, Deer, etc.	Eat flesh Example: Lion, Tiger, etc.	Feed on both plants and flesh. Example: Crow, Man, etc.	Live on or inside the host to derive nourishment. Example: Plasmodium, lice, tapeworm, etc.

3. Decomposers: The organisms which breakdown (decompose) the dead remains of plants and animals or convert complex compounds into simpler ones so that they go into the soil and are used up again by the plants are called decomposers. Example: Fungi and bacteria. Decomposers help in the replenishment of the natural resources.

4. Role of Decomposers:
Decomposers breakdown the dead remains and waste products of organisms i.e., complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants.

5. Food Chain: Food chain refers to an arrangement of different biotic groups in a sequence of energy transfer. It consists of a series of organisms feeding on one another.

6. Food web: In nature, the food chains are interconnected with each other forming a web-like pattern. This network of food chains is called a food web.

• Trophic level: Each step or level of the food chain where transfer of energy takes place is called trophic level.
• First Trophic level: Autotrophs (Producers)
• Second trophic level: Primary consumers (Herbivores)
• Third Trophic level: Secondary consumers (Small carnivores)
• Fourth Trophic level: Tertiary consumers (Larger carnivores)

7. Flow of energy between various components of the environment

• Green plants capture 1% of the sunlight that falls on their leaves.
• The flow of energy is unidirectional in a food chain.
• Ten Percent Law: About 90% of energy is used by the present trophic level in its life processes like respiration, digestion, etc. and only 10% of energy is transferred to the next trophic level.
  .
• Food chains generally consist of only three or four steps: Only 10% of energy is transferred to the next trophic level, so the loss of energy at each step is so great that very little usable energy remains after four trophic levels.
• There are generally a big population at lower trophic levels of an ecosystem. The population of the producers is the highest in a food chain.
• The relationship among organisms can be shown as a series of branching lines called a food web instead of a straight line as each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms.

8. Biological Magnification: The pesticides and other chemicals used to protect our crops from diseases and pests get either washed down into the soil or into the water bodies. They enter the food chain on being absorbed by the plants along with water and minerals from soil or on being taken up by aquatic plants and animals from the water bodies.

These get accumulated progressively at each trophic level as they are not degradable. The maximum concentration of these chemicals gets accumulated in human bodies as humans occupy the topmost trophic level in a food chain. This phenomenon is known as biological magnification. Due to this, our food grains, vegetables and fruits contain varying amounts of pesticide residues.
Ozone: Ozone (O₃) is a molecule formed by three atoms of oxygen.

9. Bad Ozone: The ozone present in the troposphere (lower parts of atmosphere) is harmful for plants and animals.

10. Good Ozone: The ozone present in the stratosphere (higher levels of the atmosphere) is beneficial as it shields the surface of the Earth from ultraviolet (UV) radiation of the Sun which is highly damaging to organisms and can cause skin cancer in human beings.

11. Formation of Ozone:
High energy UV radiation act on oxygen (O₂) molecule and split apart some molecular oxygen (O₂) into free oxygen (O) atoms. These oxygen atoms then combine with the molecular oxygen to form ozone.

12. Reason of Ozone Depletion:
Excessive use of synthetic chemicals like chlorofluorocarbons (CFCs) used as refrigerants and in fire extinguishers, caused ozone depletion in the upper atmosphere. In 1987, UNEP (United Nation Environment Programme) forged an agreement to freeze CFCs production at 1986 levels by all countries.

13. Ozone Hole: The decline of ozone layer thickness in Antarctica was first discovered in 1985 and was termed as Ozone Hole (thinning of ozone layer).

14. Management of Garbage:
Rapid industrialisation and the rise in demand of consumer goods have led to excessive garbage generation and problems of their disposal.

15. The methods of solid waste disposal are:

• Recycle: Non-biodegradable solid wastes like plastic, metal can be recycled.
• Reuse: Paper can be reused for making greeting cards, decorative articles, etc.
• Composting: Organic wastes filled into a compost pit can be converted into organic manure.
• Landfill: Wastes dumped in low lying area are compacted by rolling with bulldozers.
• Incineration: Burning wastes in incinerators.

16. Use of Disposable Paper cups: Instead of plastic cups, use of disposable cups made of clay called kulhads were suggested as an alternative. The use of kulhads on large scale results in loss of the fertile top soil. So, now disposable paper cups are being used instead of kulhads.

Class 10 Science Chapter 15 Notes Important Terms

Biodegradable substances: The substances which can be easily broken down into simpler substances by natural processes, e.g., wood, paper, etc.

Non-biodegradable substances: The substances which cannot be easily degraded into simpler substances by natural processes, e.g., plastics, DDT, etc.

Pollution: Any undesirable change in the physical, chemical or biological characteristics of air, water or soil is called pollution.

Ecosystem: The interaction of the living and non-living components of an area forms a unit called ecosystem.

Biotic: The living components of an ecosystem are called biotic. For example, predators, plants, parasites, etc.

Abiotic: The non-living components of an ecosystem are called abiotic. For example, temperature, humidity, etc.

Food chain: It is the sequence of organisms formed to transfer food energy by the act of eating or being eaten.

Food web: A network of food chains is called a food web.

Trophic level: Various steps in a food chain at which the transfer of energy takes place are called trophic levels.

Producers: The organisms which can synthesise their own food by the process of photosynthesis.

Consumers: The organisms which depend directly or indirectly on producers for their food requirements.

Decomposers: The organisms which break down the complex substances present in dead remains of plants and animals into simpler substances.

Biological magnification: The phenomenon in which the concentration of harmful toxicant goes on increasing at successive trophic levels, e.g., DDT.

On this page, you will find Sources of Energy Class 10 Notes Science Chapter 14 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 14 Sources of Energy will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 14 Notes Sources of Energy

Sources of Energy Class 10 Notes Understanding the Lesson

Characteristics of a good fuel

• High calorific value (gives more heat per unit mass).
• Bums without giving out any smoke or harmful gases.
• Proper ignition temperature.
• Cheap and easily available.
• Easy to handle, safe to transport.
• Convenient to store.
• Burns smoothly.

Classification of sources of energy

1. On the basis of use

• Conventional sources of energy.
• Non-conventional sources of energy
• Conventional sources of energy are those which are used extensively and meet a major portion of our energy requirement.
  Examples:
  (a) Fossil fuels,(b) Thermal power plant,(c) Hydropower plant,(d) Biomass,(e) Wind energy.
• Non-conventional sources of energy are those which are not used as the conventional ones and meet our energy requirements only on a limited scale.
  Examples:
  (a) Solar energy,(b) Nuclear energy,(c) Tidal and wave energy,(d) Geothermal energy

2. On the basis of quantity available

• Renewable sources of energy
• Non-renewable sources of energy
• Renewable sources of energy are those which are inexhaustible i.e., which can be replaced as we use them and can be used to produce energy again and again.
  Examples:
  (a) Solar energy,(b) Wind energy
• Non-renewable sources of energy are those which are exhaustible and cannot be replaced once they have been used.
  Examples:  (a) Fossil fuel

Conventional sources of energy
1. Fossil fuels: Fossil fuels were formed millions of year ago, when plant and animal remains got buried under the Earth and were subjected to high temperature and pressure conditions.

Examples: Coal and petroleum
These are non-renewable sources of energy:

Pollution Caused by Fossil Fuels

• Released oxides of carbon, nitrogen and sulphur (acidic in nature) which causes acid rain that damages trees, plants, reduces fertility of soil.
• Produces large amount of CO₂ in the atmosphere which causes greenhouse effect leading to excessive heating of the Earth.

Controlling Pollution Caused by Fossil Fuels

• Increasing the efficiency of the combustion process.
• Using various techniques to reduce the escape of harmful gases and ashes into the surroundings.

2. Thermal Power Plant
A power plant which uses heat energy to generate electricity.

• Burning of fossil fuels produces steam to run turbines.
• Set up (power plants) near the coal and oil fields to minimise the cost of transportation and production.
• Transmission of electricity is more efficient.

3. Hydro Power Plants

• Dams are constructed to collect water flowing in high altitude rivers. The stored water has a lot of potential energy.
• When water is allowed to fall from a height, potential energy changes to kinetic energy, which
• rotates the turbines to produce electricity.

Advantages

• No environmental pollution
• Flowing water is a renewable source of electric energy.
• Construction of dams prevents flooding of rivers, provide water for irrigation.

Disadvantages

• Large areas of agricultural land, a vast variety of flora and fauna, human settlements get submerged in the water of reservoir formed by the dam.
• Large ecosystems are destroyed.
• Vegetation that submerged under water rots under anaerobic conditions and produces large amount of methane which is a greenhouse gas.
• Creates problems of satisfactory rehabilitation of displaced people.
• Dams are highly expensive to construct.
• Dams cannot be constructed on all river sites.

4. Biomass

The dead parts of plants and trees and the waste materials of animals are called Biomass.
(i) Wood: It is a biomass and used as a fuel for a long time.
Disadvantages

• Produces a lot of smoke on burning.
• Do not produce much heat.
• Thus by improvement in technology we can improve the efficiency of traditional sources of energy.
  For example, wood can be converted into much better fuel called charcoal.

(ii) Charcoal: When wood is burnt in a limited supply of air, then water and other volatile materials gets removed and charcoal is formed.

Charcoal is a better fuel than wood because

• it has a higher calorific value than wood.
• it does not produce smoke while burning.
• it is a compact fuel, easy to handle and convenient to use.

(iii) Cow dung: It is biomass but it is not good to burn cowdung directly as fuel because it

• produces a lot of smoke.
• does not burn completely, produces a lot of ash as residue.
• has low calorific value.
  by making biogas (or gobar gas) from cow dung, we get a smokeless fuel.

(iv) Biogas: It is mixture of gases produced during decomposition of biomass in the absence of oxygen.

• Methane is major component of biogas. Biogas contains 75% methane, carbon dioxide, hydrogen and hydrogen sulphide.
• Biogas is produced in a biogas plant using animal dung, sewage, crop residues, vegetable wastes, poultry dropping, etc.

Biogas plant: Construction and Working
The plant has dome like structure built with bricks. A slurry of cow dung and water is made in the mixing tank from where it is fed into the digester. The digester is a sealed chamber in which there is no oxygen. Anaerobic microorganisms that do not require oxygen, decompose or breakdown complex compound of cow slurry and produces methane, carbon dioxide, hydrogen and hydrogen sulphide.

Advantages of Biogas

• It is an excellent fuel as it contains upto 75% methane (CH₄).
• It burns without smoke.
•  Leaves no residue like ash in wood and coal burning.
• Heating capacity is high.
• It is also used for lighting.
• Slurry left behind is used as excellent manure rich in nitrogen and phosphorus.
• Safe and efficient method of waste disposal.

5. Wind energy

• Unequal heating of the landmass and water bodies by solar radiations generate air movement and causes wind to blow.
• Kinetic energy of the wind can be used:
  o to generate electricity by turning the rotor of the turbine, o to lift water from the well, o to run flour mills.
• But the output of a single windmill is quite small so a number of windmills are erected over a large area called wind energy farm.
• The minimum wind speed for windmill to serve as a source of energy is 15-20 km/per hour.

Advantages

• Eco-friendly
• Efficient source of renewable energy
• No recurring expenses for production of electricity.

Disadvantages

• Wind energy farms need large area of land.
• Difficulty in getting regular wind speed of 15-20 km/per hour.
• Initial cost of establishing wind energy farm is very high.
• High level of maintenance of blades of windmill.

Alternate or Non-conventional Sources of Energy
Day by day, our demand for energy is increasing, so there is a need for another source of energy.

Reasons for alternate sources of energy

• The fossil fuel reserves in the Earth are limited which may get exhausted soon if we use them at the current rate.
• Reduce the pressure on fossil fuels making them last for a much longer time.
• To reduce the pollution level and to save the environment.

(i). Solar Energy

• Sun is the ultimate source of energy.
• Energy obtained from the Sun is called solar energy.
• Energy received by the Earth per second per unit area from the Sun is known as solar constant.

Solar constant = 1.4 kJ/s/m² Solar energy devices: Devices using solar energy are:

• Solar cooker
• Solar cells
• Solar water heater
• Solar Cooker

Box Type Solar Cooker: It consists of a rectangular box which is made up of wood or plastic which is painted dull black.

• Inner walls of the box are painted black to increase heat absorption.
• Solar cookers are covered with glass plate and have mirror to focus the rays of the sun and achieve higher temperature. Glass plate traps solar radiation by greenhouse effect.
• Temperature inside the box increases 100°C-140°C in 2-3 hours.

Advantages

• Save precious fuel like coal, LPG, kerosene.
• Does not produce smoke.
• Nutrients of food do not get destroyed while cooking.
• Upto four food items can be cooked at the same time.
• Renewable
• Can be used in rural areas.

Disadvantages

• Solar cookers cannot be used at night.
• If the day sky is covered with clouds, even then solar cooker cannot be used.
• Direction of reflector of solar cooker changes from time to time to keep it facing the sun.
• Solar radiations are not uniform over the Earth’s surface.
• Cannot be used for frying or baking purpose.

(ii) Solar Cell

• Solar cells convert solar energy into electricity.
• A solar cell develops a voltage of 0.5-1 V and can produce about 0.7 W of electricity.
• A large number of solar cells are combined in an arrangement called solar cell panel.

Advantages

• Have no moving parts.
• Require little maintenance.
• Can work without any focussing device.
• Can be set up in remote and inacessible areas.

Disadvantages

• Manufacturing is expensive.
• Availability of special grade silicon for making solar cells is limited.
• Silver wire for interconnection of cells is expensive.

Uses of Solar Cell

• Artificial satellites and space probes use solar cells as the main source of energy.
• Radio, TV relay stations in remote locations use solar cell panels.
• Traffic signals, calculators and many toys are fitted with solar cells.

2. Energy from the Sea

	Tidal Energy	Wave Energy	Ocean Thermal Energy
Working: (i)	The phenomenon of high and low tide give us tidal energy.	Kinetic energy of huge waves near sea shore is trapped to generate electricity.	The difference in the temperature of water at the surface and deeper section of ocean is used to obtain energy in Ocean Thermal Energy Conversion plants (OTEC).
(ii)	It is harnessed by constructing a dam across the narrow opening of the sea.	Wave energy is used for rotation of turbine and production of electricity.	The warm surface water is used to boil volatile liquid ammonia. The vapours of the liquid are used to run the turbine of generator to produce electricity.
Disadvantage:	The location where such dams can be built are limited.	Wave energy is viable only where waves are very strong.	Efficient commercial exploitation is very difficult.

3. Geothermal Energy

• ‘Geo’ means ‘earth’ and ‘thermal’ means ‘heat’.
• Geothermal energy is the heat energy from hot rocks present inside the earth.
• When underground water comes in contact with ‘hot spot’, steam is generated. Steam trapped in rocks is routed through pipes to a turbine and used to generate electricity.

Advantages

• Economical to use geothermal energy.
• Does not cause any pollution.

Disadvantages

• Geothermal energy is not available everywhere.
• Deep drilling in the earth to obtain geothermal energy is very difficult and expensive.

4. Nuclear Energy

• The energy released during a nuclear reaction is called nuclear energy.
• It can be obtained by two types of nuclear reactions:

(i) Nuclear fission
(ii) Nuclear fusion

(i) Nuclear Fission:

• ‘Fission’ means split up.
• The process in which the heavy nucleus of a radioactive atom (such as uranium, plutonium
  or thorium) split up into smaller nuclei when bombarded with low energy neutrons, is called nuclear fission.
• A tremendous amount of energy is produced.
• U-235 is used as a fuel in nuclear reactors in the form of uranium rods.

Working: In a nuclear reactor self sustaining chain reaction releases energy at a controlled rate, which is used to produce steam and further generate electricity.

(ii) Nuclear Fusion: When two nuclei of light elements (like hydrogen) combine to form a heavy nucleus (like helium) and tremendous amount of energy is released it is called nuclear fusion.

• Very-very high temperature and pressure is needed for fusion.
• Hydrogen bomb is based on this phenomenon.
• Nuclear fusion is the source of energy in the sun and other stars.

Advantages

• Production of large amount of useful energy from a very small amount of nuclear fuel.
• Does not produce greenhouse gases like C02.

Disadvantages

• Environmental contamination due to improper nuclear waste storage and its disposal.
• Risk of accidental leakage of harmful radiations.
• High cost of installation.
• Limited availability of nuclear fuel.

Environmental Consequences
Exploiting any source of energy disturbs the environment in some way or the other. Thus, the source we would choose depends upon the following factors:

• Ease of extracting energy from the source.
• Cost of extracting energy from the source.
• Efficiency of technology available to extract energy.
• The environmental damage caused by using that source.

On this page, you will find NCERT Class 10 Geography Chapter 3 Notes Pdf free download. CBSE Class 10 Social Science Notes Geography Chapter 3 SST Water Resources will seemingly, help them to revise the important concepts in less time.

Resource and Development Class 10 Notes Social Science Geography Chapter 3

CBSE Class 10 Geography Chapter 3 Notes Understanding the Lesson

1. Water is a valuable resource. It is essential for life on the earth. Human body contains 70% of water. Plants cannot grow without water. Other living beings including micro-organisms cannot survive without water.

2. Three-fourth of the earth’s surface is covered with water and water is a renewable resource. Still there are many countries and regions around the globe that suffer from acute water crisis. The reason is that only a small proportion of it accounts for freshwater (2.5 per cent) that we can put to use.

3. The freshwater is mainly obtained from surface run off and groundwater that is continually being renewed and recharged through the hydrological cycle.

4. India receives nearly 4 per cent of the global precipitation and ranks 133 in the world in terms of water availability per person per annum. By 2025, it is predicted that large parts of India will live in absolute water scarcity.

5. Although the availability of water resources varies over space and time, water scarcity in most cases is caused by over-exploitation, excessive use and unequal access to water among different social groups.

6. Water scarcity may be an outcome of large and growing population and consequent greater demand for water. A large population means more water for domestic use as well as to produce more food grain. To facilitate higher food grain production, water resources are being over-exploited to expand irrigated areas and dry-season agriculture. This leads to falling groundwater levels.

7. The growing number of industries has made matter worse by exerting pressure on existing freshwater resources. Multiplying urban centres with large and dense populations and urban lifestyles have also aggravated the problem.

8. There are many regions in India where scarcity is due to bad quality of water. Water in these regions get polluted by domestic and industrial wastes, chemicals, pesticides, and fertilisers used in agriculture.

9. Now it has become essential to conserve and manage our water resources, to safeguard ourselves from health hazards, to ensure food security and so on. Over-exploitation and mismanagement of water resources will impoverish this resource and cause ecological crisis.

10. Previously dams were seen as a way to conserve and manage water. Dams were traditionally built to impound rivers and rainwater that could be used later to irrigate agricultural fields. Today, the purpose behind building dams has been multiplied. Dams are built not just for irrigation but for electricity generation, water supply for domestic and industrial uses, flood control, etc.

11. In recent years, people have opposed multi-purpose projects and large dams due to a variety of reasons. Regulating and damming of rivers affect their natural flow causing several problems for human beings as well as for aquatic life. Also, big dams have mostly been unsuccessful in controlling floods at the time of heavy rainfall.

12. Water harvesting system is considered both socio-economically and environmentally viable. In ancient India, along with sophisticated hydraulic structures, there existed an extraordinary tradition of water-harvesting system. Roof-top rainwater harvesting was commonly practised to store drinking water particularly in Rajasthan.

13. In the semi-arid and arid regions of Rajasthan, almost all the houses traditionally had underground tanks or tankas for storing drinking water.

14. Rainwater stored in tankas can be an extremely reliable source of drinking water when all other sources are dried up, particularly in the summers.

15. Rooftop rainwater harvesting is being successfully adapted in many parts of rural and urban India to store and conserve water. Tamil Nadu is the first state in India which has made rooftop rainwater harvesting structure compulsory to all the houses across the state.

Water Resources Class 10 CBSE Notes Important Terms

Glacier: A mass or river of ice moving very slowly.

Aquifer: A layer of water-bearing rock or soil.

Dam: A barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment.

Groundwater: Water obtained from a depth of more than 15 metres.

Multi-purpose project: A large-scale hydro project serving a number of purposes such as irrigation, flood control, etc.

Rainwater harvesting: A technique of gathering, accumulating and storing of rainwater for different uses.

Hydro-electricity: Electricity produced by using water power.

Drip irrigation: A type of irrigation in which water gets dropped in the form of drips close to roots of the plants in order to conserve the moisture.

Water Scarcity: A situation in which water is not sufficiently available to meet the needs of the people.

On this page, you will find NCERT Class 10 History Chapter 8 Notes Pdf free download. CBSE Class 10 Social Science Notes History Chapter 8 SST Novels, Society and History will seemingly, help them to revise the important concepts in less time.

Novels, Society and History Class 10 Notes Social Science History Chapter 8

CBSE Class 10 History Chapter 8 Notes Understanding the Lesson

1. The novel is a form of literature, born from print. It first took firm root in England and France. Novels began to be written from the seventeenth century, but they really bloomed from the eighteenth century with the emergence of new groups of lower-middle-class people in England and France.

2. With the growth of readership and expansion of the market for books, authors began to experiment with different literary styles. Walter Scott collected popular Scottish ballads which he used in his historical novels about the wars between Scottish clans. The epistolary novel used the private and personal form of letters to tell its story. Samuel Richardson’s Pamela told much of its story through an exchange of letters between two lovers.

3. Initially, novels were costly and therefore not accessible to the poor. But the establishment of circulating libraries in 1740 solved this problem. Technological improvements in printing brought down the price of books and innovations in marketing led to expanded sales.

4. By and by novels gained popularity. While reading novels, the reader was transported to another person’s world. In rural areas, people would collect to hear one of them reading a novel aloud, often becoming deeply involved in the lives of characters. When Charles Dickens’s Pickwick Papers was serialised in a magazine in 1836, it attracted a vast number of readers.

5. Some of the nineteenth-century novels focused on the terrible effects of industrialization on people’s lives and characters. For example, Charles Dickens’s Hard Times and Oliver Twist. Emile Zola’s Germinal on the life of a young miner in France explores in harsh detail the grim conditions of miners’ lives.

6. By the eighteenth century, novels began exploring the world of women-their emotions and identities, their experiences and problems. The novels of Jane Austen give us a glimpse of the world of women in genteel rural society in the early-nineteenth-century Britain. But other women novelists such as Charlotte Bronte’s Jane Eyre dealt with women who broke established norms of society before adjusting to them.

7. Novels for young boys were full of adventure set in places remote from Europe. Books like R.L. Stevenson’s Treasure Island and Rudyard Kipling’s Jungle Book became very popular. G.A. Henty’s historical adventure novels for boys were also popular during the height of the British empire.

8. For adolescent girls, there were love stories. Novels like Ramona by Helen Hunt Jackson and a series entitled What Katy Did by Sarah Chauncey Woolsey became very popular among girls.

9. Novels became popular in India too but from the nineteenth century when Indians got familiar with the Western novel. Some of the earliest Indian novels were written in Bengali and Marathi. The earliest novel in Marathi was Baba Padmanji’s Yamuna Paryatan, which used a simple style of storytelling to speak about the plight of widows. This was followed by Lakshman Moreshwar Halbe’s.

10. Novels began appearing in south Indian languages during the period of colonial rule. O. Chandu Menon’s Indulekha was the first modern novel in Malayalam. Kandukuri Viresalingam’s Rajashekhara Caritamu was in Telugu.

11. In the north, novels began to be written in Hindi. The first proper modern Hindi novel titled Pariksha  Guru was written by Srinivas Das of Delhi. But this novel could not win many readers, as it was perhaps too moralizing in its style.

12. However, a novel-reading public in Hindi was created by the writings of Devaki Nandan Khatri. His best-seller, Chandrakanta is believed to have contributed immensely in popularising the Hindi language and the Nagari script among the educated classes of those times. But Hindi novel achieved excellence with the writing of Premchand. His novels like Sevasadan, Rangbhoomi and Godan became great hits.

13. Many of the Bengali novels were located in the past, their characters, events and love stories based on historical events. Another group of novels dealt with the social problems and romantic relationships between men and women. The popular Bengali novelists were Bankim Chandra Chattopadhyay and Sarat Chandra Chattopadhyay.

14. Novels were a valuable source of information on Indian customs and traditions. They were also meant to popularise some ideas. Writers like Viresalingam used the novel mainly to propagate their ideas about society among a wider readership. Novels also helped in creating a sense of natural pride among their readers by glorifying accounts of the past.

15. The novel was a medium of entertainment among the middle class. The circulation of printed books allowed people to amuse themselves in new ways. There was a great demand for detective and mystery novels. Reading a novel was just like daydreaming.

16. Not all welcomed novels. There were many people who advised, especially women and children to stay away from the immoral influence of novels. Some parents kept novels in the lofts in their house, out of their children’s reach. Young people often read them in secret.

17. Women did not only read novels, they also began to write them. In the early decades of the twentieth century, women in south India wrote novels and short stories.

18. By and by novels began to be written to empower women. Rokeya Hossein’s novel Padmarag showed the need for women to reform their condition by their own actions. With growing trend of writing novels or reading them among women, many men became suspicious. As a result, women began to write in secret.

19. Novels were not only written by members of the upper caste but also by the lower caste. Potheri Kunjambu was a lower caste writer from north Kerala. He wrote a novel called Saraswativijayam in 1892, mounting a strong attack on caste oppression.

20. From the 1920s, in Bengal too a new kind of novel emerged that depicted the lives of peasants and low castes. Advaita Malla Burman’s Titash Ekti Nadir Naam is an epic about the Mallas, a community of fisherfolk.

21. Vaikkom Muhammad Basheer was a Muslim novelist in Malayalam. He wrote short novels and stories in the ordinary language of conversation. His novels spoke about details from the everyday life of Muslim households. He also brought into Malayalam writing themes which were considered very unusual at that time – poverty, insanity and life in prison.

22. The novel helped in popularising the sense of belonging to a common nation. Another way was to include various classes in the novel so that they could be seen to belong to a shared world. Premchand’s novels are filled with all kinds of powerful characters drawn from all levels of society.

Novels, Society and History Class 10 CBSE Notes Important Terms

Gentlemanly classes: People who claimed noble birth and high social position.

Epistolary: A type of novel written in the form of a series of letters.

Serialized: A format in which the story is published in installments, each part in a new issue of a journal.

Vernacular: The normal, spoken form of a language rather than the formal, literary form.

Satire: A form of representation through writing, drawing, painting, etc. that provides a criticism of society in a manner that is witty and clever.

Classical: Representing an exemplary standard within a traditional and long-established form or style.

Notes of History Class 10 Chapter 8 Time Period

1740: Introduction of circulating libraries.

1749: Henry Fielding’s Tom Jones was issued in six volumes.

1836: Charles Dickens’s Pickwick Papers was serialized in a magazine.

1852: Karuna o Phulmonir Bibaran, first novel in Bengali was published.

1857: Bhudeb Mukhopadhyay’s Anguriya Binimoy, the first historical novel in Bengal was written.

1882: Srinivas Das’s novel Pariksha Guru was published. It was the first proper modern novel.

1885: Emile Zola’s Germinal was published on the life of a young miner in France.

1894: Jungle Book of Rudyard Kipling became great hits.

1905: Rokeya Hossein’s Sultana’s Dream was published. In it, she shows a topsy-turvy world in which women take the place of men.

1936: Godan was published and became Premchand’s best-known work.