CBSE Class 11 Fundamental of Physical Geography Chapter 8: Composition and Structure of Atmosphere NCERT Solutions

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This chapter delves into the essential components and structural layers of Earth's atmosphere. It covers the primary gases like nitrogen and oxygen, their proportions, and the role of trace gases such as carbon dioxide. The solutions explain the significance of different atmospheric layers, particularly the troposphere, for human life and weather phenomena. Key elements like temperature, pressure, wind, and humidity are also discussed as constituents of weather and climate. Understanding the composition, including water vapor and dust particles, is crucial for comprehending atmospheric processes. These NCERT Solutions provide clear, concise explanations and answers to help students grasp the fundamental concepts of atmospheric science, aiding in effective exam preparation and revision.

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BoardCBSE
ClassClass 11
SubjectFundamental of Physical Geography
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 8

Chapter summary

Chapter 8 of Fundamental of Physical Geography focuses on the composition and structure of the Earth's atmosphere. It details the major and minor gases present, the role of water vapor and dust particles, and the importance of different atmospheric layers like the troposphere. The solutions cover the elements of weather and climate and explain why the troposphere is vital for life and weather events. This chapter provides a foundational understanding of the atmospheric system.

Learning outcomes

  • Understand the primary gases that constitute the Earth's atmosphere.
  • Identify the role of water vapor and dust particles in atmospheric composition.
  • Explain the significance of different atmospheric layers, especially the troposphere.
  • Define the key elements of weather and climate.
  • Recognize the importance of atmospheric composition for life on Earth.

Topics covered

Paper topics

  • Atmosphere composition
  • Major atmospheric gases (Nitrogen, Oxygen)
  • Minor atmospheric gases (Carbon dioxide, Argon)
  • Water vapor
  • Dust particles
  • Atmospheric layers
  • Troposphere
  • Stratosphere
  • Mesosphere
  • Ionosphere
  • Elements of weather
  • Elements of climate

Important topics

  • Composition of the Atmosphere (Gases, Water Vapor, Dust)
  • Importance of the Troposphere
  • Role of Carbon Dioxide in Radiation Balance
  • Altitude effects on Gas Concentration
  • Elements of Weather and Climate

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Questions and Solutions

Multiple choice question

Which one of the following gases constitutes the major portion of the atmosphere?
  1. Oxygen
  2. Nitrogen
  3. Argon
  4. Carbon dioxide
Solution: The Earth's atmosphere is primarily composed of Nitrogen, which accounts for approximately 78% of its volume. Oxygen is the second most abundant gas at about 21%. Argon, Carbon dioxide, and other trace gases make up the remaining 1%. Therefore, Nitrogen constitutes the major portion.

Multiple choice question

Which atmospheric layer is important for human beings?
  1. Stratosphere
  2. Mesosphere
  3. Troposphere
  4. Ionosphere
Solution: The troposphere is the lowest layer of the atmosphere and is critically important for human beings. It is where we live, breathe, and where almost all weather phenomena occur. This layer contains the majority of the atmosphere's water vapor and dust particles, which are essential for life and weather processes.

Multiple choice question

Sea salt, pollen, ash, smoke soot, and fine soil are associated with which of the following?
  1. Gases
  2. Dust particles
  3. Water vapour
  4. Meteors
Solution: Sea salt, pollen, ash, smoke soot, and fine soil are all examples of solid particles suspended in the atmosphere. These are collectively referred to as dust particles or aerosols, which play a role in atmospheric processes like scattering sunlight and forming clouds.

Multiple choice question

At what approximate height in the atmosphere does oxygen gas become negligible in quantity?
  1. 90 km
  2. 120 km
  3. 100 km
  4. 150 km
Solution: As altitude increases, the density of the atmosphere decreases, and the concentration of gases like oxygen also diminishes significantly. Oxygen becomes negligible in quantity at approximately 120 km above the Earth's surface.

Multiple choice question

Which one of the following gases is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation?
  1. Oxygen
  2. Nitrogen
  3. Helium
  4. Carbon dioxide
Solution: Carbon dioxide (CO2) is a significant greenhouse gas. It allows shortwave incoming solar radiation to pass through the atmosphere relatively unimpeded. However, it absorbs and re-emits longwave outgoing terrestrial (heat) radiation, trapping heat and contributing to the Earth's temperature regulation.

Answer the following questions in about 30 words

(i) What do you understand by atmosphere?

Solution: The atmosphere is the envelope of gases surrounding the Earth, held by gravity. It contains essential life-supporting gases like oxygen for animals and carbon dioxide for plants, and it protects us from harmful solar radiation.

(ii) What are the elements of weather and climate?

Solution: The primary elements that define weather and climate are temperature, atmospheric pressure, wind speed and direction, humidity (the amount of water vapor in the air), cloud cover, and precipitation (like rain, snow, or hail).

(iii) Describe the composition of atmosphere.

Solution: The atmosphere is composed of a mixture of gases, primarily nitrogen and oxygen. It also contains smaller amounts of other gases like argon and carbon dioxide, along with variable amounts of water vapor and suspended dust particles.

(iv) Why is troposphere the most important of all the layers of the atmosphere?

Solution: The troposphere is the most important layer because it is the lowest layer where all life exists. It contains most of the atmosphere's water vapor and dust, making it the layer where all weather and climate changes occur, directly impacting all living organisms.

Answer the following questions in about 150 words

1. Describe the composition of the atmosphere.

Solution: The Earth's atmosphere is a complex mixture comprising several components. The most abundant constituents are gases, with nitrogen making up about 78% and oxygen about 21% of the dry air. These two gases are vital for life on Earth. The remaining 1% consists of other gases, including argon (about 0.93%), carbon dioxide (about 0.04%), and trace amounts of neon, helium, krypton, hydrogen, and ozone. In addition to gases, the atmosphere contains significant amounts of water vapor, which varies greatly by location and altitude, typically ranging from near 0% in cold, dry regions to about 4% in hot, humid areas. Water vapor is crucial for weather phenomena like clouds and precipitation. Furthermore, the atmosphere contains suspended solid and liquid particles, known as dust particles or aerosols. These include sea salt, fine soil, smoke, soot, and volcanic ash. These particles play roles in scattering solar radiation and acting as nuclei for cloud droplet formation, influencing atmospheric visibility and climate.

Common mistakes

  • Confusing the proportions of major atmospheric gases.
  • Underestimating the importance of trace gases like CO2.
  • Not clearly distinguishing between the functions of different atmospheric layers.
  • Failing to list all essential elements of weather and climate.

Revision tips

  • Memorize the percentage composition of major atmospheric gases.
  • Focus on the unique characteristics and importance of the troposphere.
  • Create flashcards for the elements of weather and climate.
  • Review the role of non-gaseous components like water vapor and dust.

Practice MCQs

Q1. Which gas forms the largest proportion of the Earth's atmosphere?

Q2. The atmospheric layer most crucial for human existence and weather phenomena is:

Q3. What are aerosols like sea salt, pollen, and smoke soot examples of?

Q4. At what approximate altitude does oxygen become negligible in the atmosphere?

Q5. Which gas is transparent to incoming solar radiation but traps outgoing terrestrial radiation, contributing to the greenhouse effect?

Frequently asked questions

What is the atmosphere?

The atmosphere is the layer of gases that surrounds the Earth, held in place by gravity. It is composed of various gases, water vapor, and dust particles, and is essential for life.

What are the main gases in the Earth's atmosphere?

The main gases are Nitrogen (about 78%) and Oxygen (about 21%). Other gases like Argon, Carbon dioxide, and trace gases make up the remaining 1%.

Why is the troposphere considered the most important layer for humans?

The troposphere is the lowest layer where all weather phenomena occur, and it contains the oxygen necessary for respiration and the water vapor essential for life. Most biological activity takes place here.

What are the elements of weather and climate?

The primary elements include temperature, atmospheric pressure, winds, humidity, clouds, and precipitation.

How do dust particles affect the atmosphere?

Dust particles, along with sea salt and smoke soot, are suspended in the atmosphere and play a role in scattering solar radiation and acting as condensation nuclei for cloud formation.

What is the significance of carbon dioxide in the atmosphere?

Carbon dioxide is important because it is transparent to incoming solar radiation but opaque to outgoing terrestrial radiation, acting as a greenhouse gas that helps regulate Earth's temperature.

Important links

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