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NCERT Solutions Class 11 Geography Chapter 7 Composition and Structure of Atmosphere: In Chapter 7 of NCERT Solutions for Class 11 Geography, we learn about the atmosphere’s composition and structure. This means understanding what gases make up the air around us and how they’re arranged in different layers.
This Class 11 Geography Chapter 7 NCERT solution was carefully developed using easy-to-understand language while adhering to the guidelines for solving NCERT Solutions for Class 11. Working through these solutions can be highly beneficial for students in their board exams, as well as in preparing for future competitive Exams.
NCERT Solutions Class 11 Geography Chapter 7: Composition and Structure of Atmosphere
Page No 64
Can you imagine what will happen to us in the absence of ozone in the atmosphere?
Without the protective ozone layer in the atmosphere, life on Earth would face significant challenges due to increased exposure to harmful ultraviolet (UV) radiation from the sun. Here are some consequences:
- Increased Risk of Skin Cancer: UV radiation can cause DNA damage in skin cells, leading to an increased risk of skin cancer, including melanoma, squamous cell carcinoma, and basal cell carcinoma.
- Eye Damage: Prolonged exposure to UV radiation can damage the eyes, leading to conditions such as cataracts, which may impair vision and require surgical intervention.
- Weakened Immune System: UV radiation can suppress the immune system, making individuals more susceptible to infections and diseases.
- Impact on Plants: UV radiation can harm plant life by affecting photosynthesis, leading to reduced crop yields and disruptions in ecosystems.
- Harm to Marine Life: UV radiation can penetrate the ocean’s surface, harming marine organisms such as phytoplankton, which form the base of the marine food chain.
- Climate Change: Changes in UV radiation can also impact atmospheric chemistry and climate patterns, potentially leading to shifts in weather patterns and global climate change.
Exercises Page No: 66
1. Multiple choice questions.
(i) Which one of the following gases constitutes the major portion of the atmosphere?
(a) Oxygen
(b) Nitrogen
(c) Argon
(d) Carbon dioxide
Answer:
(b) Nitrogen
(ii) Atmospheric layer important for human beings is:
(a) Stratosphere
(b) Mesosphere
(c) Troposphere
(d) Ionosphere
Answer:
(c) Troposphere
(iii) Sea salt, pollen, ash, smoke soot, fine soil — these are associated with:
(a) Gases
(b) Dust particles
(c) Water vapour
(d) Meteors
Answer:
(b) Dust particles
(iv) Oxygen gas is in negligible quantity at the height of atmosphere:
(a) 90 km
(b) 120 km
(c) 100 km
(d) 150 km
Answer:
(b) 120 km
(v) Which one of the following gases is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation?
(a) Oxygen
(b) Nitrogen
(c) Helium
(d) Carbon dioxide
Answer:
(d) Carbon dioxide
2. Answer the following questions in about 30 words.
(i) What do you understand by atmosphere?
The atmosphere is the layer of gases surrounding a planet, held in place by gravity. It plays a vital role in regulating temperature, weather patterns, and supporting life.
(ii) What are the elements of weather and climate?
The elements of weather and climate include temperature, humidity, precipitation, atmospheric pressure, wind speed and direction, and cloud cover.
(iii) Describe the composition of atmosphere.
The atmosphere is composed of gases, primarily nitrogen (78%) and oxygen (21%), with trace amounts of other gases such as carbon dioxide, argon, and water vapor.
(iv) Why is troposphere the most important of all the layers of the atmosphere?
The troposphere is the most important layer of the atmosphere because it contains almost all of the Earth’s weather and is where most of the Earth’s atmospheric phenomena, such as clouds, precipitation, and storms, occur. It directly affects life on Earth and supports various ecosystems.
3. Answer the following questions in about 150 words.
(i) Describe the composition of the atmosphere.
The atmosphere is composed of gases, water vapor, and dust particles. Nitrogen and oxygen together make up 99% of the atmosphere, with nitrogen at 78.08% and oxygen at 20.95%. Other gases include argon, carbon dioxide, neon, helium, krypton, xenon, and hydrogen in smaller amounts. As we move higher in the atmosphere, the proportion of gases changes. For instance, oxygen becomes negligible at about 120 km height, while carbon dioxide and water vapor are found only up to 90 km.
Carbon dioxide plays a important role in the greenhouse effect by absorbing and reflecting terrestrial radiation. Ozone, found in the atmosphere, absorbs harmful ultraviolet rays from the sun, protecting the Earth’s surface.
(ii) Draw a suitable diagram for the structure of the atmosphere and label it and describe it.
The atmosphere is divided into five layers based on temperature variations:
- Troposphere: The lowest layer, extending up to 8 km at the poles and 18 km at the equator. It contains dust particles and water vapor, where weather changes occur. Temperature decreases with altitude.
- Stratosphere: Found above the tropopause (troposphere’s boundary), extending up to 50 km. It contains the ozone layer, absorbing harmful ultraviolet radiation.
- Mesosphere: Above the stratosphere, up to 80 km. Temperature decreases with altitude, reaching about -100°C at 80 km. Its upper limit is the mesopause.
- Thermosphere: The outermost layer, starting from 80 km with no definite upper limit. It’s very hot due to solar radiation. The ionosphere, within it, reflects radio waves.
- Exosphere: The highest layer above the thermosphere, gradually merging with outer space. It’s sparse and little is known about it.
NCERT Solutions Class-11 Geography Chapter-7: Composition and Structure of Atmosphere Summary
The atmosphere is like a blanket of air that wraps around the Earth. It’s made up of different gases like nitrogen, oxygen, argon, carbon dioxide, and others. Nitrogen is the most abundant gas, making up about 78% of the atmosphere, followed by oxygen at around 21%. The atmosphere is divided into layers based on temperature changes. The lowest layer is the troposphere, where weather happens. Above that is the stratosphere, which contains the ozone layer that protects us from harmful UV rays. The mesosphere is next, where meteors burn up. Then comes the thermosphere, where it’s very hot due to solar radiation. Lastly, there’s the exosphere, which merges with outer space. Each layer has its own unique characteristics and plays a role in regulating Earth’s climate and protecting life.
NCERT Solutions Class-11 Geography Chapter-7: Composition and Structure of Atmosphere- FAQs
What is the atmosphere?
The atmosphere is a layer of gases surrounding the Earth. It contains various gases like nitrogen, oxygen, carbon dioxide, and others.
What are the main components of the atmosphere?
The main components of the atmosphere are nitrogen (about 78%), oxygen (about 21%), argon, carbon dioxide, and trace gases like neon, helium, and methane.
How is the atmosphere structured?
The atmosphere is divided into layers based on temperature changes. These layers are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
What is the significance of the ozone layer?
The ozone layer is located in the stratosphere and absorbs harmful ultraviolet (UV) radiation from the Sun, protecting life on Earth from its damaging effects.
Why is the troposphere important?
The troposphere is where weather occurs and is the layer closest to the Earth’s surface. It contains most of the atmosphere’s water vapor and plays a important role in supporting life on Earth.
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