Consider the following statements regarding the composition of the atmosphere: 1. The proportion of gases remains constant up to the highest layers of the atmosphere. 2. Nitrogen is the most abundant gas in the atmosphere. 3. Nitrogen and Oxygen make up the bulk of the atmosphere. Which of the statements given above is/are correct?

The correct option is 2 and 3 only. Explanation The atmosphere is a mixture of various gases, water vapour, and dust particles. While the major gases maintain a relatively stable ratio in the lower atmosphere, the composition varies significantly with altitude. - Statement 1 is Incorrect: The proportion of gases does not remain constant up to the highest layers. The atmosphere is divided into two broad zones based on composition: - The Homosphere (up to approximately 80 km), where the proportion of major gases is uniform. - The Heterosphere (above 80 km), where gases separate into distinct layers based on their molecular weight and density. Additionally, gases like carbon dioxide and water vapour are concentrated in the lower layers and decrease rapidly with height. - Statement 2 is Correct: Nitrogen is the most abundant gas in the atmosphere, accounting for approximately 78.08% of the total volume. - Statement 3 is Correct: Nitrogen (78.08%) and Oxygen (20.95%) collectively constitute roughly 99% of the total volume of clean, dry air. The remaining 1% includes Argon (0.93%), Carbon Dioxide (0.036%), and trace gases such as Neon, Helium, and Ozone. Key Takeaway: Nitrogen and Oxygen make up 99% of the atmosphere's volume. The uniformity of this gaseous mixture is maintained only in the lower atmosphere (homosphere), whereas the upper atmosphere (heterosphere) exhibits stratification.

NCERT Class 11 Geography — Chapter 1: Composition and Structure of Atmosphere

mcqeasy

Consider the following statements regarding the composition of the atmosphere:

The proportion of gases remains constant up to the highest layers of the atmosphere.
Nitrogen is the most abundant gas in the atmosphere.
Nitrogen and Oxygen make up the bulk of the atmosphere.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A2 and 3 only
B1, 2 and 3
C2 only
D1 and 2 only

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Solution

The correct option is 2 and 3 only.

Explanation

The atmosphere is a mixture of various gases, water vapour, and dust particles. While the major gases maintain a relatively stable ratio in the lower atmosphere, the composition varies significantly with altitude.

Statement 1 is Incorrect: The proportion of gases does not remain constant up to the highest layers. The atmosphere is divided into two broad zones based on composition:
- The Homosphere (up to approximately 80 km), where the proportion of major gases is uniform.
- The Heterosphere (above 80 km), where gases separate into distinct layers based on their molecular weight and density.
Additionally, gases like carbon dioxide and water vapour are concentrated in the lower layers and decrease rapidly with height.
Statement 2 is Correct: Nitrogen is the most abundant gas in the atmosphere, accounting for approximately 78.08% of the total volume.
Statement 3 is Correct: Nitrogen (78.08%) and Oxygen (20.95%) collectively constitute roughly 99% of the total volume of clean, dry air. The remaining 1% includes Argon (0.93%), Carbon Dioxide (0.036%), and trace gases such as Neon, Helium, and Ozone.

Key Takeaway: Nitrogen and Oxygen make up 99% of the atmosphere's volume. The uniformity of this gaseous mixture is maintained only in the lower atmosphere (homosphere), whereas the upper atmosphere (heterosphere) exhibits stratification.

Your note

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In the context of the structure of the atmosphere, consider the following statements regarding the Troposphere: 1. The temperature in this layer increases with height. 2. Its thickness is greatest at the equator and least at the poles. 3. It is devoid of dust particles and water vapour. Which of the statements given above is/are correct?

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The correct option is 2 and 3 only.

Explanation

Statement 1 is Incorrect: The proportion of gases does not remain constant up to the highest layers. The atmosphere is divided into two broad zones based on composition:
- The Homosphere (up to approximately 80 km), where the proportion of major gases is uniform.
- The Heterosphere (above 80 km), where gases separate into distinct layers based on their molecular weight and density.
Additionally, gases like carbon dioxide and water vapour are concentrated in the lower layers and decrease rapidly with height.
Statement 2 is Correct: Nitrogen is the most abundant gas in the atmosphere, accounting for approximately 78.08% of the total volume.
Statement 3 is Correct: Nitrogen (78.08%) and Oxygen (20.95%) collectively constitute roughly 99% of the total volume of clean, dry air. The remaining 1% includes Argon (0.93%), Carbon Dioxide (0.036%), and trace gases such as Neon, Helium, and Ozone.