With reference to the Earth's atmosphere, which one of the following statements is correct?
- (a) The total amount of insolation received at the equator is roughly about 10 times of that received at the poles.
- (b) Infrared rays constitute roughly two-thirds of insolation.
- (c) Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere. ✓ UPSC's answer
- (d) Infrared waves are a part of visible spectrum of electromagnetic waves of solar radiation.
Why the answer is (c)
• Option (c) is correct: the infrared part of solar radiation is largely absorbed by water vapour, which is concentrated in the lower troposphere, along with carbon dioxide; this is a key part of the greenhouse effect.
• Hence option (c).
Why the other options are wrong
- (a) The total amount of insolation received at the equator is roughly about 10 times of that…
- The equator receives about twice, not ten times, the polar insolation.
- (b) Infrared rays constitute roughly two-thirds of insolation.
- Infrared is a little under half of insolation, not two-thirds.
- (d) Infrared waves are a part of visible spectrum of electromagnetic waves of solar radiation.
- Infrared is outside the visible spectrum.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2023, held on 28 May 2023. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.