UPSC Physical Geography – Chapter 10: The Atmosphere – Composition and Structure (22 MCQs)

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UPSC Physical Geography – Chapter 10: The Atmosphere – Composition and Structure (22 MCQs) – 22 questions, subject: Geography. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  

The most abundant gas in the atmosphere by volume is:

Correct Answer: D [nitrogen]

Explanation:

78.08 per cent.

2.  

The ozone layer lies mainly in the:

Correct Answer: B [stratosphere]

Explanation:

Ozone is concentrated mainly between about 10 and 50 km, which lies within the stratosphere.

3.  

Almost all weather phenomena take place in the:

Correct Answer: C [troposphere]

Explanation:

The troposphere holds almost all the water vapour and dust and has strong convection, so clouds, rain and storms form there.

4.  

Radio waves transmitted from the Earth are reflected back by the:

Correct Answer: D [ionosphere]

Explanation:

The ionosphere, about 80 to 400 km, contains electrically charged ions that reflect radio waves back to the Earth.

5.  

The normal lapse rate of temperature in the troposphere is about:

Correct Answer: A [6.5 °C per km]

Explanation:

about 1 °C for every 150–165 m; NCERT gives both 6.5 °C per 1,000 m and 1 °C per 165 m (≈6.1 °C per km).

6.  

According to NCERT, the temperature at the tropopause over the equator is about:

Correct Answer: B [−80 °C]

Explanation:

NCERT gives the tropopause temperature as about −80 °C over the equator and about −45 °C over the poles.

7.  

Water vapour in the air is highest in the:

Correct Answer: D [warm and wet tropics]

Explanation:

up to 4 per cent.

8.  

Dust and salt particles in the atmosphere are important because they:

Correct Answer: A [act as hygroscopic nuclei for condensation]

Explanation:

Dust and salt particles are hygroscopic: water vapour condenses around them to form cloud droplets.

9.  

The temperature at the top of the mesosphere (about 80 km) is about:

Correct Answer: D [−100 °C]

Explanation:

(d) Correct (NCERT).

10.  

Consider the following statements:

1. The troposphere is thicker at the equator than at the poles.
2. Temperature generally decreases with height in the troposphere.
3. Temperature decreases with height throughout the stratosphere.

Which of the statements given above is/are correct?

Correct Answer: B [1 and 2 only]

Explanation:

The troposphere is thicker at the equator (18 km) than at the poles (8 km) and cools with height; the stratosphere warms with height.

11.  

Assertion (A): The ozone layer is vital for life on the Earth.

Reason (R): Ozone absorbs most of the harmful ultra-violet radiation from the Sun.

Correct Answer: A [Both A and R are true, and R is the correct explanation of A]

Explanation:

Both are true, and absorbing harmful ultra-violet radiation is exactly why the ozone layer is vital for life.

12.  

The share of argon in the atmosphere by volume is about:

Correct Answer: C [0.93 per cent]

Explanation:

Argon, an inert gas, makes up about 0.93 per cent of the air by volume, the third largest share.

13.  

The outermost layer of the atmosphere, which merges with space, is the:

Correct Answer: B [exosphere]

Explanation:

The exosphere lies above the ionosphere; its very thin air gradually merges with outer space.

14.  

Which gas is transparent to incoming solar radiation but absorbs outgoing terrestrial radiation?

Correct Answer: A [Carbon dioxide]

Explanation:

Carbon dioxide lets incoming short-wave solar radiation through but absorbs outgoing long-wave terrestrial radiation, causing the greenhouse effect.

15.  

The mesopause separates the:

Correct Answer: C [mesosphere and the ionosphere (thermosphere)]

Explanation:

The mesopause, at about 80 km, is the upper limit of the mesosphere, above which the ionosphere (thermosphere) begins.

16.  

The Kigali Amendment to the Montreal Protocol deals with:

Correct Answer: B [hydrofluorocarbons]

Explanation:

The Kigali Amendment of 2016 commits parties to phase down hydrofluorocarbons, potent greenhouse gases that replaced CFCs.

17.  

Arrange the following in chronological order:

1. Montreal Protocol signed
2. India Meteorological Department set up
3. Kigali Amendment adopted
4. Stratosphere identified

Select the correct answer using the code given below:

Correct Answer: C [2-4-1-3]

Explanation:

1875, 1902, 1987, 2016.

18.  

The aurora is seen in the:

Correct Answer: B [ionosphere (thermosphere)]

Explanation:

Auroras occur roughly 100 to 300 km up, where charged solar particles excite gases in the ionosphere (thermosphere).

19.  

Jet aircraft often prefer to fly in the lower stratosphere because it is:

Correct Answer: A [largely free of clouds and weather disturbances]

Explanation:

The lower stratosphere lies above most clouds and convection, giving smooth flying conditions for jet aircraft.

20.  

The concentration of carbon dioxide in the atmosphere in 2024 was about:

Correct Answer: D [420 ppm]

Explanation:

The WMO global mean for 2024 was 423.9 ppm, which is about 420 ppm among the options.

21.  
UPSC Prelims 2025

Consider the following statements:

Statement I: The amount of dust particles in the atmosphere is more in subtropical and temperate areas than in equatorial and polar regions.

Statement II: Subtropical and temperate areas have less dry winds.

Which one of the following is correct in respect of the above statements?

Correct Answer: C [Statement I is correct but Statement II is not correct]

Explanation:

dust is more in these areas because of dry winds, so Statement II is wrong.

22.  
UPSC Prelims 2024

With reference to "water vapour", which of the following statements is/are correct?

1. It is a gas, the amount of which decreases with altitude.
2. Its percentage is maximum at the poles.

Select the answer using the code given below:

Correct Answer: A [1 only]

Explanation:

water vapour is maximum in the warm, wet tropics, not at the poles.

➤ Full notes, maps, tables, a reason for every option and Mains PYQs – U08 · Physical Geography (UPSC book, ₹249): www.shanmugamiasacademy.in/study-materials/upsc-physical-geography

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