With reference to the Earth's atmosphere, which one of the following statements is correct?

With reference to the Earth's atmosphere, which one of the following statements is correct?
  1. The total amount of insolation received at the equator is roughly about 10 times of that received at the poles.
  2. Infrared rays constitute roughly two-thirds of insolation.
  3. Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere.
  4. Infrared waves are a part of visible spectrum of electromagnetic waves of solar radiation.

Solution

Per the official UPSC key, the answer is B. Statement C — water vapour in lower atmosphere absorbs IR — is the textbook-correct statement; most coaching keys marked C. UPSC officially marked B.

Asked in: UPSC Prelims 2023

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