2012 GS Paper I, all questions
UPSC Prelims 2012 · GS Paper I
Question 62: Environment and Ecology
The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs
athe water vapour of the air and retains its heat
bthe ultraviolet part of the solar radiation
call the solar radiations
dthe infrared part of the solar radiation
AnswerUPSC’s answer is (d).
Carbon dioxide is a greenhouse gas: it is transparent to incoming shortwave sunlight but absorbs infrared (heat) radiation, mostly the heat re-radiated by the Earth, and traps it. More carbon dioxide means more heat is retained, warming the atmosphere. It does not absorb water vapour, nor all radiation, and ultraviolet is mainly absorbed by ozone.
Why each option is right or wrong
- (a) Wrong: carbon dioxide does not absorb water vapour.
- (b) Wrong: ultraviolet is mainly absorbed by ozone.
- (c) Wrong: carbon dioxide absorbs only certain wavelengths, mainly infrared, not all radiation.
- (d) Correct: carbon dioxide absorbs infrared radiation and retains heat.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2012, General Studies Paper I, Series A. The paper on upsc.gov.in.