Bhagya – Page 27 – Jharkhand Board Solution

JAC Class 9 Science Important Questions and Answers in Hindi & English Jharkhand Board

September 17, 2024September 16, 2024 by Bhagya

JAC Jharkhand Board Class 9th Science Important Questions in Hindi & English Medium

JAC Board Class 9th Science Important Questions in English Medium

JAC Board Class 9th Science Important Questions in Hindi Medium

JAC Class 9 Science Solutions in Hindi & English Jharkhand Board

September 17, 2024September 16, 2024 by Bhagya

JAC Jharkhand Board Class 9th Science Solutions in Hindi & English Medium

JAC Board Class 9th Science Solutions in English Medium

JAC Board Class 9th Science Solutions in Hindi Medium

JAC Class 9 Maths Notes Chapter 11 रचनाएँ

October 11, 2024September 10, 2024 by Bhagya

Students should go through these JAC Class 9 Maths Notes Chapter 11 रचनाएँ will seemingly help to get a clear insight into all the important concepts.

JAC Board Class 9 Maths Notes Chapter 11 रचनाएँ

रचनाएँ (Constructions ) : प्रमेय सिद्ध करते समय या उन पर आधारित प्रश्नों को हल करते समय जो आकृतियाँ बनाते हैं, वे साधारण चित्र होते हैं। इन चित्रों में इतनी परिशुद्धता नहीं होती। लेकिन ज्यामितीय रचनाओं में ज्यामितीय यन्त्रों जैसे अंशांकित रूलर, चाँदा (protractor), सेट स्क्वायर, परकार, इत्यादि का प्रयोग आवश्यक होता है। ज्यामितीय रचना में तर्क और कौशल का समावेश होता है। रचना यथार्थ और शुद्ध (accurate) होती है।

रचना करते समय ध्यान रखना चाहिए कि

आकृति शुद्ध और स्वच्छ हो, रबर (eraser) का कम-से-कम प्रयोग करना चाहिए। किसी भी रचना से पूर्व सम्बन्धित आकृति का कच्चा चित्र बना लेने से रचना करना सुगम हो जाता है।
रचना से सम्बन्धित समस्त बिन्दु तथा रेखाएँ स्पष्ट तथा यथा सम्भव चौड़ाई रहित होने चाहिए।
रचना हेतु खींची गयी सहायक रेखाओं को बिन्दु रेखाओं (dotted lines) द्वारा तथा मुख्य रेखाओं को अधिक स्पष्ट खींचना चाहिए।
रचना के समस्त पद क्रमशः लिखे जाने चाहिए।

त्रिभुजों की रचनाएँ (Constructions of Triangles) : प्रत्येक त्रिभुज में छ: अवयव होते हैं, तीन भुजाएँ और तीन कोण। इन प्रतिबन्धों के अनुसार त्रिभुज की रचना करने के लिए कम से कम तीन स्वतन्त्र अवयव आवश्यक होते हैं :

तीन भुजाएँ, या
दो भुजाएँ और उनके बीच का कोण, या
दो कोण और एक भुजा, या
समकोण त्रिभुज में कर्ण और एक भुजा।

JAC Class 9 Science Notes Chapter 1 Matter in Our Surroundings

September 10, 2024September 9, 2024 by Bhagya

JAC Board Class 9th Science Chapter 1 Notes Matter in Our Surroundings

→Matter: Everything in this universe is made up of material which is called matter. Matter is anything that has mass and occupies space. Matter is made up of lots of tiny particles.

→ Characteristics of particles of matter:
a. Particles of matter have space between them.
b. Particles of matter are continuously moving.
c. Particles of matter attract each other. Matter exists in three different states, viz., solid, liquic and gas.

Solid	Liquids	Gas
1. Strong intermolecular force of attraction.	1. Weak intermolecular force of attraction.	1. Very weak intermolecular force of attraction.
2. Very less intermolecular space.	2. Large intermolecular space.	2. Very large intermolecular space.
3. Have definite shape and volume.	3. No definite shape but definite volume.	3. No definite shape and volume.
4. High density, high melting and boiling points.	4. Density is lower, low melting and boiling points.	4. Density is very low.
5. Solids cannot be compressed.	5. Liquids can be compressed.	5. Gases are highly compressible.
6. Solids cannot flow.	6. Liquids can flow.	6. Gases can flow.

→ Matter can change its state from solid to liquid and from liquid to gas and vice-versa.
JAC Class 9 Science Notes Chapter 1 Matter in Our Surroundings 2

→ Effect of Temperature: On increasing temperature, the particles gain energy and start vibrating with greater energy. Due to increased kinetic energy, the particles overcome the force of attraction and a new state is obtained.

→ Melting Point: It is the temperature at which a solid becomes a liquid at atmospheric pressure. Boiling Point: It is the temperature at which a liquid changes into its vapour form at atmospheric pressure.

→ Latent Heat of Fusion: The amount of heat energy required to change 1 kg of a solid into liquid at its melting point is called the latent heat of fusion of the solid.

→ Latent Heat of Vaporisation: The amount of heat energy required to change 1 kg of a liquid into vapour at atmospheric pressure, at its boiling point is called the latent heat of vaporisation of the liquid.

→ Sublimation: It is the change of state directly from solid to gas or vice-versa without going through the liquid state. Evaporation: It is a surface phenomenon in which a liquid changes into vapour/gas below its boiling point. It results in lowering of temperature, i.e., cooling is caused when evaporation takes place.

→ Factors affecting Evaporation: An increase in surface area increases the rate of evaporation. An increase in temperature increases the rate of evaporation. A decrease in humidity increases the rate of evaporation. An increase in wind speed increases the rate of evaporation.

→ Some measurable quantities and their units:

Quantity	SI Unit	A Symbol
Temperature	kelvin	K
Length	metre	m
Mass	kilogram	kg
Weight	newton	N
Volume	cubic metre	m³
Density	kilogram per cubic metre	kg/m³
Pressure v	pascal	Pa

JAC Class 9 Science Notes

JAC Class 10 Social Science Notes Economics Chapter 5 Consumer Rights

September 10, 2024September 9, 2024 by Bhagya

JAC Board Class 10 Social Science Notes Economics Chapter 5 Consumer Rights

→ We the people participate in the market both as producers and consumers. As producers of goods and services we could be working in any of the sectors such as agriculture, industry, or services. Consumers participate in the market when they purchase goods and services that they need.

Rules and regulations are required for the protection of the consumers in the marketplace. Individual consumers often find themselves in a weak position.
Exploitation in the marketplace happens in various ways. For example, sometimes traders indulge in unfair trade practices, such as, when shopkeepers weigh less than what they should or when traders add charges that were not mentioned before, or when adulterated/defective goods are sold.
Markets do not work in a fair manner when producers are few and powerful whereas consumers purchase in small amounts and are scattered. This happens especially when large compnîes are producing these goods.

→ Consumer Movement

The consumer movement arose out of dissatisfaction of the consumers as many unfair practices were being indulged in by the sellers.
It vas presumed that it was a consumer’s responsibility while buying various products.
In Inda, the consumer movement as a ‘social force’ originated with the necessity of protecting and promoting the interests of consumers against unethical and unfair trade practices.
A major step taken in 1986 by the Indian government was the enactment of the Consumer Protection Act 1986, popularly known as COPRA.

→ Consumer Rights Safety is Everyone’s Right

We as consumers, have the right to be protected against the marketing of goods and delivery of services that are hazardous to life and property.
Many goods and services that we purchase, require special attention to safety. For example, pressure cookers have a safety valve which, if it is defective, can cause a serious accident. The manufacturers of the safety valve have to ensure high quality.
Information about goods and services: Consumers have the right to be informed about the particulars of goods and services that they purchase. Consumers can then complain and ask for compensation or replacement if the product proves to be defective in any manner. For example, if we buy a product and find it defective well within the expiry period, we can ask for a replacement. If the expiry period is not printed, the manufacturer will blame the shopkeeper and will not accept the responsibility.
In October 2005, the Government of India enacted a law, popularly known as RTI (Right to Information) Act, which ensures its citizens all the information about the functions of government departments.

→ Where should consumers go to get justice?

Consumers have 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.
Consumer forums: The consumer movement in India has led to the formation of various organisations locally known as consumer forums or consumer protection councils. They guide consumers on how to file cases in the consumer court. On many occasions, they also represent individual consumers in the consumer courts. These voluntary organisations also receive financial support from the government for creating awareness among the people.
Under COPRA, a three-tier quasi-judicial machinery at the district, state and national levels was set up for redressal of consumer disputes.
The district level court deals with the cases involving claims upto ₹ 20 lakh, the state level courts between ₹ 20 lakh and ₹ 1 crore and the national level court deals with the cases involving claims exceeding ? 1 crore.
If a case is dismissed in district level court, the consumer can also appeal in State and then in National level courts.
Thus, the Act has enabled us as consumers to have the right to represent in the consumer courts.

→ Learning to Become Well-Informed Consumers

The enactment of COPRA has led to the setting up of separate departments of Consumer Affairs in Central and State governments.
The posters are one example through which government spread information about legal process which people can use. You might also be seeing such advertisements on television channels.

→ Taking the Consumer Movement Forward

India has been observing 24 December as the National Consumers’ Day. It was on this day that the Indian Parliament enacted the Consumer Protection Act in 1986. India is one of the countries that have exclusive courts for consumer redressal.
Today there are more than 700 consumer groups in the country of which only about 20-25 are well organised and recognised for their work.
After more than 25 years of the enactment of COPRA, consumer awareness in India is spreading, but slowly.

JAC Class 10 Social Science Notes

JAC Class 10 Social Science Notes Economics Chapter 4 Globalisation and the Indian Economy

September 10, 2024September 9, 2024 by Bhagya

JAC Board Class 10 Social Science Notes Economics Chapter 4 Globalisation and the Indian Economy

→ Today’s consumers have a variety of choice of goods and services. Markets have been transformed vastly in a matter of few years.

→ Production Across Countries

Until the middle of the twentieth century, production was largely organised within countries.
Trade wa§ the main channel connecting distant countries.
Multinational corporations (MNCs) emerged. A MNC is a company that owns or controls production in more than one country.
MNCs set up offices and factories for production in regions where they get cheap labour and other resources. This is done to reduce the cost of production and the MNCs can earn greater profits.
MNCs not only sell their products globally but also produce the goods and services globally.
Production process is spread across the world witji cost optimisation.

→ Interlinking Production Across Countries

MNCs have set up production close to the markets; wherein skilled and unskilled labour is available at low costs and the availability of other factors of production is assured.
The money that is spent to buy assets, such .as land, building, machines and other equipment is called investment. Any Investment made by MNCs is called foreign investment.
At times MNCs set up production in collaboration with local companies. The benefit of the local companies is two¬fold: MNCs provide finance for additional investments. MNCs might bring with them the latest technology for production.
The most common route for MNC investments is to buy up local companies and then to expand production. Secondly, large MNCs in developed countries place orders for production with small producers of garments, footwear, sports items, etc. The products are supplied to MNCs, which then they sell under their own brand names to the customers. These MNCs have tremendous power to determine price, quality, delivery, and labour conditions for these distant producers.
MNCs are exerting a strong influence on production at these distant locations. Therefore, production in these widely dispersed locations is getting interlinked.

→ Foreign Trade and Integration of Markets

For a long time foreign trade has been the main channel connecting the countries. Trade routes connected India and South Asia to markets both in East and West, and extensive trade took place along these routes.
Foreign trade creates an opportunity for the producers to reach beyond domestic markets. Buyers have a wide option to choose from the imported goods produced in another country.
More choices of goods in the market and prices of similar goods in the two markets tend to become equal. Producers in the two countries closely compete against each other even though they are separated by thousands of miles.
Foreign trade, thus, integrates the markets in different countries.

→ What is Globalisation?

Globalisation is the process of rapid integration or interconnection between countries.
More and more goods and services, investments and technology are moving between countries. Globalisation has also encouraged movement of people between countries.

→ Factors that have Enabled Globalisation

Rapid improvement in technology has been one rpajor factor that has boosted the globalisation process. In the past fifty years, there have been several improvements in technology which have made faster delivery of goods across long distances possible at lower costs.
There have been huge advancements in information and communication technology. Information can be obtained and shared instantly.
The Indian government, after Independence had put barriers to foreign trade and foreign investment to protect the producers within the country from foreign competition. Starting around 1991, government removed the trade barriers. The time had come for the producers to compete with the producers around the globe. The government thought that this would enable the producers to impro ve’ the performance and the quality of the produce.
The goods could be imported or exported more easily and also foreign companies could set up factories and offices in India. This is known as liberalisation.

→ World Trade Organisation:

The aim of World Trade Organisation (WTO) is to liberalise international trade. Powerful international organisations believe that barriers to foreign trade and investment are harmful. Trade between the countries should be ‘free’.
WTO establishes rules of international trade and sees that these rules are followed. It is seen that the developed countries have unfairly retained trade barriers, while WTO has forced the developing nations to remove trade barriers.

→ Impact of Globalisation in India

Globalisation has affected the lives of the people and the economy in both positive and negative way.
MNCs have increased their investments in India over the past 20 years. MNCs have been interested in industries, such as cell phones, automobiles, electronics, soft drinks, fast food or service such as banking in urban areas. These products have large number of well-off buyers. In these industries, new jobs have been created. Local companies supplying raw materials, etc., to these industries have prospered.
Top Indian companies have benifited from increased competition as they have been able to invest in newer technologies and raise their production standards. Some have gained from the collaborations with foreign companies.
Few large Indian companies, such as Tata Motors, Infosys, Ranbaxy, Sundaram Fasteners, Asian Paints, etc., have emerged as multinationals themselves.
Governments in India are setting up special industrial zones, known as SEZs to encourage investments by foreign companies and help them establish their offices in India. Labour laws have been made flexible. Companies are allowed to hire workers on a temporary
basis, instead of on a regular basis. This lowers the cost of production and MNCs are able to make profits.
The jobs of workers are no longer secure. They do not have regular work. When they are employed, they have to put in long hours of work and also may have to do night shift. Their wages are low.
A large number of small producers had to shut down their units because of stiff competition from MNCs. They have been rendered jobless. Conditions of work in the organised sector have come to resemble the unorganised sector.

→ Struggle for a Fair Globalisation

Fair globalisation would create opportunities for all, and also ensure that the benefits of globalisation are shared better.
The government can play a major role in making globalisation fair. Its policies should protect not only the rich but also the poor and small producers in the country. The government can ensure that the labour laws are implemented and followed, and the labourers get their rights. It can support the small producers till they become capable of competing in the market with MNCs.
The government should ensure that the WTO rules are free and applied fairly across the world.

JAC Class 10 Social Science Notes

JAC Class 10 Social Science Notes Economics Chapter 3 Money and Credit

September 10, 2024September 9, 2024 by Bhagya

JAC Board Class 10 Social Science Notes Economics Chapter 3 Money and Credit

→ Money as a Medium of Exchange

A person holding money can exchange it for any commodity or service that he or she might want.
Thus everyone prefers to receive payments in money and then exchange the money for things that they want.
Both parties have to agree to sell and buy each other’s commodities. This is known as Double Coincidence of Wants.
What a person desires to sell is exactly what the other wishes to buy.
In a barter system where goods are directly exchanged without the use of money, the Double Coincidence of Wants is an essential feature.
In an economy where money is in use, by providing the crucial intermediate step it eliminates the need for Double Coincidence of Wants.
Money acts as an intermediate in the exchange process. It is called a medium of exchange. This is known as Barter System.

→ Modern Forms of Money

Money acts as a medium of exchange in transactions.
Before the introduction of coins, a variety of things were used as money.
For example, since the very early ages, Indians used grains and cattle as money.

→ Currency

Modem forms of money include currency – paper notes and coins.
Money is accepted as a medium of exchange because the currency is authorized by the government of the country.
In India, the Reserve Bank of India issues currency notes on behalf of the government of India.
As per Indian law, no other individual or organization is allowed to issue currency.
No individual in India can legally refuse payment made in rupees.

→ Deposits with Bank

The other form in which people hold money is ‘deposits with the bank’.
People deposit money with the banks by opening a bank account in their name.
Banks accept deposits and also pay an amount as interest on the deposits.
People also have the provision to withdraw the money as and when they require.
Since the deposits in the accounts can be withdrawn on demand, these deposits are called demand deposits.
Some payments are made by cheques instead of cash. For payment by cheque, the buyer who has an account with the bank, prepares a cheque for a specific amount.
A cheque is a paper instructing the bank to pay a specific amount from the holder’s account to the person in whose name the cheque has been issued.
The facility of cheque against demand deposits makes it possible to directly settle payments without the use of cash.
Since demand deposits are accepted widely as a means of payment, along with currency, they constitute money in the modem economy.
But for the banks, there would be no demand and no payments by cheques against these deposits. The modem forms of money – currency and deposits – are closely linked to the working of the modem banking system.

→ Loan Activities of Banks

Banks keep only a small proportion of their deposits as cash with themselves.
This is kept as a provision to pay the depository who might come to withdraw money from the bank on any given day.
Since, on any particular day, only some of its many depositors come to withdraw cash, the bank is able to manage with this cash.
Banks use the major portion of the deposits to extend loans to the individuals for their requirements.
There is a huge demand for loans for various economic activities.
Banks mediate between those who have surplus funds and those who are in need of these funds.
Banks charge a higher interest rate on loans than what they offer on deposits.
The difference between what is charged from the borrowers and what is paid to the depositors is their main source of income.

→ Terms of Credit

Every loan agreement specifies an interest rate which the borrower must pay to the lender along with the repayment of the principal amount, lenders may demand collateral against the loan.
Collateral is an asset that the borrower owns and uses this as a guarantee to a lender until the loan is repaid.
The interest rate, collateral, documentation requirement, and the mode of repayment is called the terms of credit.

→ Formal Sector Credit in India

People obtain loans from various sources.
The various types of loans can be grouped as formal sector and informal sector loans.
Between these two sectors, former sector includes loans from banks and cooperatives.
The informal lenders include moneylenders, traders, employers, relatives and friends, etc.
The Reserve Bank of India supervises the functioning of formal sources of loans.
For instance, we have seen that the banks maintain a minimum cash balance out of the deposits they receive.
The RBI monitors the banks in actually maintaining a cash balance.
Periodically, banks have to submit information to the RBI on how much they are lending, to whom, at what interest rate, etc.
There is no organization that supervises the credit activities of lenders in the informal sector.
They can lend at whatever interest rate they choose.
There is no one to stop them from using unfair means to get their money back.
Compared to the formal lenders, most of the informal lenders charge a much higher rate of interest on loans.
Thus, the cost to the borrower of informal loans is much higher.
The higher cost of borrowing means that, a large part of the earnings of the borrowers is used to repay the loans.
Cheap and affordable credit is crucial for the country’s development.

→ Formal and Informal Credit

85% of the loans taken by the poor households in the urban areas are from informal sources.
Urban households take only 10% of loans from informal sources, while 90% from formal sources.
The rich households avail a cheap credit from the formal sources whereas the poor households have to pay a large amount of borrowing.
The formal sources still meet only about half of the total credit needs of the rural people.
The remaining credit needs are fulfilled by the informal sources.
Thus, it is necessary that banks and cooperatives increase their lending particularly in the rural areas so that the dependence on informal sources of credit reduces.
While formal sector loans need to expand, it is also necessary that everyone receives these loans.
It is important that the formal credit is distribute^ more equally so that the poor can benefit from the cheaper loans.

→ Self-Help Groups for the Poor

Poor -households are still dependent on informal sources of credit.
Banks are not present everywhere in rural India.
Even when they are present, getting a loan from a bank is much more difficult than getting a loan from informal sources.
The absence of collateral is one of the major reasons which prevents the poor from getting bank loans.
Informal lenders such as moneylenders, know the borrowers personally and are often willing to give a loan without collateral.
However, the moneylenders charge very high rates of interest, keep no records of the transactions and harass the poor borrowers.
In recent years, people had tried out some newer ways of providing loans to the poor like Self Help Groups (SHGS), Grameen Banks, etc.

JAC Class 10 Social Science Notes

JAC Class 10 Social Science Notes Economics Chapter 2 Sectors of Indian Economy

September 10, 2024September 9, 2024 by Bhagya

JAC Board Class 10 Social Science Notes Economics Chapter 2 Sectors of Indian Economy

→ Economy is best understood when the different economic activities are classified in different sectors.

→ Primary, secondary, tertiary, private, public, organized and unorganized are different sectors of economy in which economic activities are grouped.

→ Primary sector produces products that forms the base of other industries. This sector is also called agriculture and related sector.

→ In secondary sector those activities are covered in which through ways of manufacturing natural products are changed into other forms. This sector is also called as industrial sector.

→ The third sector is the tertiary sector. In this activities that help in the development of the primary and secondary sectors are grouped. This sector is also called service sector.

→ To know the contribution of each sector in an economy the value of final goods and services produced by each sector in a particular year is considered.

→ The total production in three sectors in a year is what is known as Gross Domestic Product (GDP) of a country. The value of GDP indicates the size of the economy.

→ In India, GDP is calculated by Central Government ministry.

→ Historically, it has been observed that countries, which are developed today had strong primary sector in the initial stage of development and eventually the manufacturing and service sectors developed.

→ In India, more people are engaged in agricultural sector than secondary and tertiary sector, however the contribution of secondary and tertiary sector in GDP is more than the primary sector. This is mainly because more people in agriculture sector are underemployed. Underemployed is also known as disguised unemployment because as those underemployed may work but not to their full capacity and earn very less. Besides primary, secondary and tertiary sector, economic activities can be grouped under organized and unorganized sectors. Organized sector covers those activities, enterprises or places of work where the terms of employment are regular and people have assured work. They are registered by the government and have to follow its rules and regulations.

→ Unorganized sector covers those activities, which generally are outside the control of government. Jobs here are often irregular and low paid. Employment is not secure in this sector.

→ Mostly people from backward communities, scheduled tribes and castes work in unorganized sector.

→ Another way of classification of economic activities is on the basis of ownership such as private and public sectors. In the public sector, the government owns most of the assets and the services. In the private sector, the ownership of assets and delivery of services is in the hands of private individuals or companies. Such as railways are under public sector and Reliance Industries is a private sector entity.

→ There are many activities, which are government’s responsibility and government needs to spend on them for human development.

JAC Class 10 Social Science Notes

JAC Class 10 Social Science Notes Economics Chapter 1 Development

September 10, 2024September 9, 2024 by Bhagya

JAC Board Class 10 Social Science Notes Economics Chapter 1 Development

→ Development has many aspects. Development goal and aspiration for everyone is different.

→ Every person can have different developmental goals. What may be development for one may not be development for the other. It may even be destructive for the other. Two people may have same but conflicting goals.

→ Earning better income, may be the aspiration of many; however people also seek things like equal treatment, freedom, security, and respect of others. They resent discrimination. All these are also important goals. People look for mix of goals.

→ Even the notion of national development could be different for every individual, different person could have different as well as conflicting notions of a country’s development.

→ National development means development for all sections of the society.

→ To compare development of different countries or a state’s per capita income is considered to be one of the most important attribute.. Per capita income is calculated on the basis of total income of the country divided by the total population.

→ In 2006, World Bank in its World Development report classified the countries as devejoped or less developed on the basis of the average income or per capita income of the country. Countries with per capita income of US $ 12,056 per annum and above in 2017, are called rich countries and those with per capita income of US $ 955 or less are called low-income countries. India comes in the category of low middle income countries because its per capita income in 2017 was just US $ 1820 per annum.

→ While average incomes are useful for comparison, but they also hide disparities within the country or a state. Even though the level of income is important, yet it is an inadequate measure of the level of development. Besides income, quality of life, education status, infant mortality rate, health standard, security, freedom and sustainability of environment are some basic criteria, to access development of an area or a region.

→ Human Development Report published by UNDP compares countries based on the educational levels of the people, their health status and per capita income. It is the people, their health, their well-being, that is most important aspect of human development. The other important aspect is sustainability of development. Sustainable development means to meet the demand of the current generation without compromising on the of the future generation resources.

→ Sustainable development is possible when we judiciously utilize the natural resources (both renewable and non-renewable) without impacting the ecological balance. Sustainability is important to enjoy the benefits of development in future as well.

JAC Class 10 Social Science Notes

JAC Class 9 Science Notes Chapter 13 Why Do We Fall Ill

September 10, 2024September 9, 2024 by Bhagya

JAC Board Class 9th Science Chapter 13 Notes Why Do We Fall Ill

→ Health: Health is a state of being free from illness or injury. According to the World Health Organisation (WHO), health is defined as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

→ Conditions essential for Good Health:

Balanced and nutritious diet.
Personal hygiene.
Clean environment and surroundings.
Healthy and pollution free air in the surroundings.
Regular exercise.
Proper rest.
Good standard of living and economic status.

→ Disease: When the body is not at ease, i.e., comfortable, it is said to have a disease. In this condition, the functioning or appearance of one or more systems of the body changes. Depending on the duration, diseases are classified as acute or chronic.
a. Acute diseases: The diseases which last for a short duration of time are called acute diseases. Being of short duration, the acute diseases are unable to cause major ill effects on health, for example, common cold, malaria, typhoid, etc.

b. Chronic diseases: The diseases which last for a long duration of time or even for a lifetime are called chronic diseases. As these diseases remain in the body for a long time, their effects on the body are severe, e.g., diabetes, tuberculosis, etc.

→ Causes of a disease:
a. Immediate cause: The organisms that enter our body and cause diseases are called immediate causes, for example, virus, bacteria, protozoa, etc.

b. Contributory cause: The secondary factors which cause these organisms to enter our body are called contributory causes, e.g., dirty water, unclear surroundings, contaminated food, improper nourishment, poverty, poor standard of living, etc.

→ Diseases may be infectious or non- infectious
a. Infectious diseases: Diseases, where microbes are the immediate cause, are called infectious diseases. The infectious diseases spread from one person to another.
b. Non-infectious diseases: Some diseases that do not spread in the community but remain internal are called non-infectious diseases. Example: cancer, genetic abnormalities, high blood pressure, etc.

→ Infectious diseases: When a disease causing organism enters our body, it causes infection. It multiplies and grows in the body of the host.

Pathogen	Diseases
Bacteria	Tuberculosis, tetanus, typhoid, cholera
Virus	AIDS, polio, chickenpox, rabies, measles
Fungi	Skin diseases, food poisoning
Protozoan	Malaria, amoebiasis, kala-azar
Worm	Filariasis

→ Infectious diseases spread through:

Air: This occurs through the little droplets thrown out by the infected person who sneezes or coughs. Someone standing closeby can breathe in these droplets and the microbes get a chance to start a new infection. Examples: common cold, pneumonia, tuberculosis.
Water: This occurs if excreta of someone suffering from an infectious disease, such as cholera, gets mixed with the drinking water used by the people nearby. The cholera causing microbes will enter new hosts through the water they drink and cause disease in them.
Contact: Many diseases spread by contact of the infected person with the healthy person. Examples: fungal infection, scabies, etc. AIDS and syphilis spread by sexual contact.
Body fluids: Infected body fluids like blood, semen, mother’s milk etc., when in contact, can also cause diseases. Example-AIDS.

→ Antibiotics: Antibiotics are the drugs that kill bacteria. They commonly block the biochemical pathways important for bacteria. Many bacteria make a cell wall to protect themselves. The antibiotic penicillin blocks the bacterial processes that build the cell wall. As a result, the growing bacteria become unable to make cell walls and die easily.

→ Inflammation: When an active immune system releases many cells at the affected tissue to kill-off the disease-causing microbes, it is called inflammation. Local effects caused in the body due to inflammation are – swelling, pain, fever and redness.

→ Principles of Treatment: There are two methods for the treatment of diseases:
a. by reducing the symptoms of the diseases.
b. by killing the microbes.

→ Principles of Prevention: These are the ways to prevent the diseases.
a. General ways: The general ways of preventing infections mostly relate to preventing exposure to the diseases. We can prevent exposure to the infectious microbes as follows:

For air-borne infections: We can prevent exposure by providing living conditions that are not over crowded.
For water-borne infections: We can prevent exposure by using safe drinking water. This can be done by treating the water for any microbial contamination.
For vector-borne infections:

We can prevent exposure by providing clean environment which are free from mosquitoes, flies, rats, etc.
Another general way of preventing the diseases is the availability of proper and sufficient food for everyone. This will help the immune system to become healthy and work properly for fighting off the microbes causing the disease.

b. Specific ways: By giving vaccines, i.e., childhood immunisation that is given to the children for preventing infectious diseases. During vaccination, we put dead or weakened pathogens in the body that mimics antigens we want to vaccinate against. This does not actually cause the disease but this would prevent any further exposure to the infecting microbes from turning into actual disease. Vaccinations are available for the following diseases: tetanus, diphtheria, whooping cough, measles, polio, rabies, etc.

JAC Class 9 Science Notes

JAC Class 9 Science Notes Chapter 12 Sound

September 10, 2024September 9, 2024 by Bhagya

JAC Board Class 9th Science Chapter 12 Notes Sound

→ Sound: Sound is a form of energy which produces a sensation of hearing in our ears.

→ Production of Sound: Sound is produced due to the vibration of objects. Vibration is a periodic back-and-forth motion of the particles of an elastic body or medium about a central position. It is also called as oscillation.
For example:
a. Strings of a guitar vibrate to produce sound when stretched.
b. When membrane of a table is struck, it vibrates to produce sound.

→ Propagation of Sound
a. The travelling of sound is called propagation of sound. Sound is propagated by the to and fro motion of particles of the medium.

b. When an object vibrates, the particles in the medium vibrate. The particle in contact with the vibrating object is first displaced from its equilibrium position. Each particle disturbs the other particle in contact. Thus, the disturbance is carried from the source to the listener.
JAC Class 9 Science Notes Chapter 12 Sound 1
c. Only the disturbance produced by the vibrating body travels through the medium, but the particles do not move forward themselves. Sound waves cannot travel in vacuum.

→ Medium: The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid or gas. Air is the most common medium for sound propagation.

→ Wave: Wave is a disturbance in which energy is transferred from one point to another without any direct contact between them.
For example: heat, light and sound are considered as waves.

→ Types of Waves
On the basis of direction of propagation, waves are categorised into two types:
a. Longitudinal waves: These are the waves in which the particles of the medium vibrate along the direction of propagation of the wave. For example: sound wave.
b. Transverse waves: In this type of wave, the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave. For example: waves produced in a stretched string.

Another type of waves which do not require any medium for propagation are called electromagnetic waves. These waves can travel through vacuum. For example, light waves and X-rays.

→ Compressions and Rarefactions

Compression is the part of wave in which particles of the medium are close to one another forming a region of high pressure and density. Compressions are represented by the upper portion of the curve called crest.
Rarefaction is the part of wave where particles spread out to form a region of low pressure and density. Rarefactions are represented by the lower portion of the curve called trough.

JAC Class 9 Science Notes Chapter 12 Sound 2

→ Wavelength: Distance between two consecutive crests or troughs is called wavelength. Wavelength is represented by λ (lambda) and its SI unit is metre.

→ Frequency: Number of oscillations of a sound wave per unit time is called its frequency. The number of crests or troughs per unit of time will give the frequency. Its SI unit is hertz (Hz).

→ Time period: The time taken to complete one vibration is called time period. It is denoted by ‘T’. Its SI unit is second (s). The frequency of a wave is the reciprocal of the time period.
v = $\frac{1}{\mathrm{~T}}$; where v is the frequency and T is the time period.

→ Amplitude: The magnitude ofthe maximum disturbance in the medium, on either side of the mean value, is called the amplitude of the wave. It is usually represented by the letter ‘A’. Its unit is metre.

→ Velocity: The distance travelled by a wave in one second is called velocity of the wave or speed of the wave. Its SI unit is metre per second (m s^-1).
Velocity = $\frac{\text { Distance travelled }}{\text { Time taken }}$
v = $\frac{\lambda}{\mathrm{T}}$, where λ = wavelength of the wave travelled and T is the time period.
v = λv (As $\frac{1}{\mathrm{~T}}$ = v, where v is called frequency of the wave)
Thus, Velocity = Wavelength × Frequency
v = λv is called the wave equation.

→ Pitch and Loudness of Sound
a. Pitch: It represents shrillness or flatness of sound. It depends on the frequency of vibration. The higher the frequency of sound wave, the higher will be the pitch of sound and vice-versa.
b. Loudness: It is the measure of the sound energy reaching the ear per second. It depends on the amplitude of the sound wave. It is measured in decibel ‘dB’.

→ Music and Noise
a. Music: It is the sound that is pleasant to hear. For example, sound coming from the musical instruments.
b. Noise: It is the sound that is unpleasant to hear. For example, sound produced by vehicles.

→ Tone and Note
a. Tone: A pure sound of single frequency is called tone.
b. Note: An impure sound produced by a mixture of many frequencies is called a note. For example, a musical note has tones of various frequencies.

→ Audible Frequency: The audible range of human ear is 20 Hz to 20,000 Hz, i.e., human ear can hear only those waves whose frequencies fall between 20 Hz and 20,000 Hz.

→ Infrasonic sound: Sound whose frequency is less than 20 Hz is called infrasonic sound. Ultrasonic sound: Sound whose frequency is more than 20,000 Hz is called ultrasonic sound.

→ Uses of ultrasonic sound: Ultrasonic sound is used to clean objects like electronic components, to detect cracks in metal blocks, in ultrasound scanners for getting images of internal organs of the human body, to break small stones formed in the kidneys into fine grains, etc.

→ Reflection of Sound: Sound reflects off a surface in the same way as light reflects and follows the same rules of reflection. Hard surfaces reflect sound better than the soft ones.

→ Laws of reflection of sound

The directions in which the sound is incident and reflected make equal angles with the normal to the reflecting surface at the point of incidence.
The incident sound wave, the reflected sound wave and the normal all, lie in the same plane.
The reflection of sound has many applications such as stethoscopes, horns, megaphones, designing of concert halls, etc.

→ Echo: In bigger monuments and in large empty halls, you can hear reflections of your sound after you speak something. This effect is known as echo. For hearing a distinct echo, the time interval between the original sound and the reflected one must be at least 0.1 s.

Since the speed of sound in air is 344 m/s, the distance travelled by sound in 0.1 s is 34.4 m. So, to hear an echo clearly and distinctly, the minimum distance of the reflecting surface from the source of sound should be half of this distance, i.e., 17.2 m.

→ Reverberation: The persistence of sound in an auditorium as a result of repeated reflections of sound is called reverberation.

→ Sonar: It is a device which uses ultrasonic waves to measure the distance, direction and speed of underwater objects. The distance of the object can be calculated by knowing the speed of sound in water and the time taken between the transmission and reception of ultrasound.
JAC Class 9 Science Notes Chapter 12 Sound 3

→ Structure of the human ear: The sound waves pass through the ear canal onto a thin membrane called eardrum. The eardrum vibrates and the vibrations are amplified by the three bones of the middle ear called malleus, incus and stapes. Middle ear then transmits the sound waves to the inner ear. The brain then interprets the signals as sound.
JAC Class 9 Science Notes Chapter 12 Sound 4

→ Supersonic speed: When a body moves in air with a speed greater than the speed of sound, it is said to have a supersonic speed.

→ Shock wave: When a supersonic aircraft moves through air, it leaves behind itself a conical region of disturbance which spreads continuously. Such a disturbance is called a shock wave. Shock waves travel at supersonic speeds and carry a huge amount of energy.