1. What is atmosphere? Explain its composition with the help of a pie diagram.
Answer:
The atmosphere is a blanket of air that surrounds the Earth. It is held around the Earth by gravity. It protects life from harmful solar radiation, helps maintain the Earth’s temperature, and plays an important role in weather and climate.
The atmosphere is made up of a mixture of gases. Its main composition is:
| Gas | Percentage |
|---|---|
| Nitrogen | 78% |
| Oxygen | 21% |
| Argon | 0.93% |
| Carbon dioxide | 0.04% |
| Other gases | 0.03% |
The atmosphere also contains water vapour and dust particles, which help in cloud formation and rainfall.
For the pie diagram, draw a circle and show the largest part as Nitrogen 78%, the second largest part as Oxygen 21%, and very small parts as Argon, Carbon dioxide, and other gases.
2. Draw a labelled diagram of the structure of atmosphere.
Answer:
Draw the layers of the atmosphere from the Earth’s surface upwards in this order:
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
Also label the following features:
- Troposphere — weather occurs here
- Stratosphere — ozone layer and aeroplanes
- Mesosphere — meteors burn here
- Thermosphere — auroras and radio waves
- Exosphere — outermost layer with very thin air
The atmosphere is divided into layers on the basis of changes in temperature and air density with height.
3. Which are the four main seasons of India?
Answer:
According to the Indian Meteorological Department, India has four main seasons:
- Winter season — December to early April
- Summer or pre-monsoon season — April to June or July
- Monsoon or rainy season — June to September
- Post-monsoon or retreating monsoon season — October to December
India has a tropical monsoon type of climate, so these seasons are mainly influenced by temperature, winds, and monsoon rainfall.
4. Why do you not feel the pressure of the atmosphere?
Answer:
We do not feel the pressure of the atmosphere because air presses on our body from all sides. At the same time, the pressure inside our body is almost equal to the atmospheric pressure outside. These two pressures balance each other. Therefore, we do not feel the force of atmospheric pressure on our body.
5. In which layer of the atmosphere do aeroplanes fly and why?
Answer:
Aeroplanes usually fly in the stratosphere. This layer is suitable for flying because it is mostly free from clouds and weather disturbances. The air in the stratosphere is more stable, so aeroplanes can fly smoothly and safely.
6(a). Distinguish between the troposphere and stratosphere.
Answer:
| Troposphere | Stratosphere |
|---|---|
| It is the lowest layer of the atmosphere. | It lies above the troposphere. |
| Its average height is about 12 km. | It extends up to about 50 km. |
| Weather phenomena like rainfall, fog, clouds, and hail occur here. | It is mostly free from clouds and weather disturbances. |
| Temperature decreases with height. | It contains the ozone layer, which protects us from harmful ultraviolet radiation. |
| The air we breathe is found here. | Aeroplanes usually fly in this layer. |
6(b). Distinguish between the south-west monsoon and north-east monsoon.
Answer:
| South-west monsoon | North-east monsoon |
|---|---|
| It is also called the summer monsoon. | It is also called the winter monsoon. |
| It blows from sea to land. | It blows from land to sea. |
| It occurs mainly from June to September. | It occurs mainly from October to February. |
| It brings most of the rainfall in India. | It generally brings less rainfall to most parts of India. |
| It is caused when land heats faster than the sea, creating low pressure over land. | It is caused when land cools faster than the sea, creating high pressure over land. |
| It brings rain from the Arabian Sea and Bay of Bengal branches. | It gives rainfall mainly to the south-eastern coast, especially Tamil Nadu and Andhra Pradesh, after picking moisture from the Bay of Bengal. |
7.1. Re-arrange the 10 stations according to their distance from the equator.
Answer:
The Table 3.3 data is not visible in the uploaded chapter pages, so this answer is based on the usual 10 representative stations used for this activity.
From nearest to farthest from the equator:
- Thiruvananthapuram
- Bengaluru
- Chennai
- Mumbai
- Nagpur
- Kolkata
- Shillong
- Jodhpur
- Delhi
- Leh
7.2(a). Find out two stations with the most extreme climate.
Answer:
The two stations with the most extreme climate are Leh and Jodhpur.
Leh has very cold winters due to its high altitude and location in the Himalayas. Jodhpur has very hot summers and low rainfall because it lies in the desert region of Rajasthan. Both places have a large difference between summer and winter temperatures.
7.2(b). Find out two stations influenced by retreating monsoons.
Answer:
The two stations influenced by retreating monsoons are Chennai and Thiruvananthapuram.
The north-east or retreating monsoon winds pick up moisture from the Bay of Bengal and bring rainfall mainly to the south-eastern coast of India, especially Tamil Nadu and nearby regions.
7.2(c)(i). Find out the two hottest stations in the month of February.
Answer:
The two hottest stations in February are Thiruvananthapuram and Chennai.
These stations are located close to the equator and near the sea, so they remain warm even during winter.
7.2(c)(ii). Find out the two hottest stations in the month of June.
Answer:
The two hottest stations in June are Jodhpur and Delhi.
Both are located in north-western India, where summers are very hot due to distance from the sea and strong heating of land during the pre-monsoon and summer season.
7.3(a). Why does Shillong experience more rainfall than Kolkata?
Answer:
Shillong receives more rainfall than Kolkata because it is located in the hilly region of Meghalaya. Moisture-laden winds from the Bay of Bengal branch of the south-west monsoon strike the hills and are forced to rise. As the air rises, it cools and causes heavy rainfall. This is called orographic rainfall.
Kolkata also receives monsoon rainfall, but it is located in the plains, so the rainfall is less compared to Shillong.
7.3(b). Why does Delhi receive more rainfall than Jodhpur?
Answer:
Delhi receives more rainfall than Jodhpur because Delhi is more influenced by the Bay of Bengal branch of the south-west monsoon. Jodhpur lies in the dry desert region of western Rajasthan, where monsoon winds become weak and carry less moisture.
Also, the Aravalli range runs almost parallel to the direction of the south-west monsoon winds, so it does not effectively block and lift the winds to cause heavy rainfall in western Rajasthan. Therefore, Jodhpur receives less rainfall than Delhi.
7.4(a). Why does Thiruvananthapuram have an equable climate?
Answer:
Thiruvananthapuram has an equable climate because it is located near the sea and close to the equator. The sea has a moderating effect on temperature, so the place does not become very hot in summer or very cold in winter. Sea breeze and land breeze also help in keeping the temperature moderate throughout the year.
According to the table, the temperature of Thiruvananthapuram remains almost between 26°C and 29°C throughout the year. This shows that it has a very small annual range of temperature.
7.4(b). Why does Chennai have more rainfall only after the monsoon is over in most parts of the country?
Answer:
Chennai receives more rainfall after the monsoon is over in most parts of India because it is mainly affected by the north-east monsoon or retreating monsoon.
During this season, winds blow from land to sea. While crossing the Bay of Bengal, these winds pick up moisture and bring rainfall to the south-eastern coast of India, especially Tamil Nadu. Since Chennai is located on this coast, it receives heavy rainfall mainly in October and November.
7.4(c). Why does Leh have moderate precipitation almost throughout the year?
Answer:
Leh receives small amounts of precipitation almost throughout the year because it is located in the high-altitude Himalayan region. It does not receive much rainfall from the south-west monsoon because it lies in the rain-shadow region beyond the Himalayas.
However, Leh receives light precipitation in different months due to western disturbances and occasional snowfall. That is why its rainfall is not concentrated in one season but is spread in small amounts throughout the year.
So, Leh has low but fairly regular precipitation throughout the year.
7.5. Despite these differences across regions, can you observe any substantial evidence to conclude that the monsoons provide a very strong framework, lending overall climatic unity to the whole country?
Answer:
Yes, despite regional differences in temperature and rainfall, the monsoon provides a strong climatic unity to India. Most parts of India receive the major share of their annual rainfall from the south-west monsoon between June and September. The arrival of the monsoon affects almost the whole country in a seasonal pattern.
The monsoon controls agriculture, water supply, rivers, reservoirs, festivals, transport, and daily life in India. Farmers in different regions depend on monsoon rainfall for sowing and growing crops. Even though some places receive heavy rainfall and some receive less rainfall, the seasonal cycle of summer, monsoon, retreating monsoon, and winter is experienced across the country.
Thus, the monsoon acts as a common climatic factor that connects different regions of India and gives the country an overall climatic unity.
8. Collect pictures of houses and clothing of people from different regions of India. Examine whether they reflect any relationship with the climatic conditions or the relief of those regions.
Answer:
Yes, houses and clothing of people in different regions of India show a clear relationship with the climate and relief of those regions.
| Region | Houses | Clothing | Relationship with climate/relief |
|---|---|---|---|
| Ladakh / Himalayan region | Houses have thick walls and small windows. | People wear woollen clothes. | The climate is very cold, so houses and clothes help in keeping people warm. |
| Himachal Pradesh / Kashmir | Houses often have sloping roofs. | People wear woollen clothes, jackets, and caps. | Sloping roofs allow snow and rainwater to slide down easily. |
| Rajasthan | Houses have thick walls, flat roofs, and small windows. | People wear loose cotton clothes and turbans. | The climate is hot and dry, so houses remain cool and clothes protect from heat and dust. |
| Kerala / Coastal areas | Houses have sloping roofs and good ventilation. | People wear light cotton clothes. | Heavy rainfall and humidity require roofs that drain water quickly and clothes that are comfortable in humid weather. |
| Assam / North-East India | Houses are often built on stilts using bamboo and wood. | People wear light clothes suitable for humid conditions. | Stilt houses protect people from floods and heavy rainfall. |
| Northern Plains | Houses are usually made of brick and cement. | People wear cotton clothes in summer and woollen clothes in winter. | The region has extreme summers and winters, so clothing changes according to season. |
Therefore, we can say that the design of houses and the clothing of people are strongly influenced by the climate, rainfall, temperature, and relief of a region.