2024 GS Paper I, all questions

UPSC Prelims 2024 · GS Paper I

Question 1: Geography

Consider the following statements :

  1. Statement-IThe atmosphere is heated more by incoming solar radiation than by terrestrial radiation.
  2. Statement-IICarbon dioxide and other greenhouse gases in the atmosphere are good absorbers of long wave radiation.

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

aBoth Statement-I and Statement-II are correct and Statement-II explains Statement-I
bBoth Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
cStatement-I is correct, but Statement-II is incorrect
dStatement-I is incorrect, but Statement-II is correct

AnswerUPSC’s answer is (d).

The atmosphere is heated mainly by terrestrial (long wave) radiation, not directly by incoming sunlight. Short wave insolation passes largely through the air and warms the earth's surface; the surface then gives off long wave heat, which carbon dioxide, water vapour and other greenhouse gases absorb. So Statement-I is wrong and Statement-II is right. Remember: the atmosphere is heated from below.

  • I. The air gains more heat from long wave radiation given off by the earth than directly from the sun.
  • II. Carbon dioxide and other greenhouse gases absorb long wave radiation well.

How you could have got this

If you were sure Statement-I is not correct, only (d) is left: every other option says it is correct.

What you needed to know: The air gains more heat from long wave radiation given off by the earth than directly from the sun.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong
  • (a) Wrong: Statement-I is incorrect, so there is nothing for Statement-II to explain.
  • (b) Wrong: Statement-I is not correct, so both cannot be correct.
  • (c) Wrong: it reverses the truth. Statement-I is the incorrect one.
  • (d) Right: the air is heated more by earth's long wave radiation, and greenhouse gases do absorb long wave radiation.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2024, General Studies Paper I, Series A. The paper on upsc.gov.in.