UPSC Prelims 2024 · GS Paper I
Question 12: Geography
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 :
AnswerUPSC’s answer is (a).
Water vapour is concentrated in the lower atmosphere, so its amount decreases with altitude; most of it lies within the troposphere. Its share is highest in the warm, moist tropics, where it can reach about 4 per cent of the air by volume, and lowest over cold, dry polar regions, so Statement 2 is wrong. Remember: water vapour decreases from the equator towards the poles.
- 1. Water vapour is concentrated near the surface and decreases with altitude.
- 2. Water vapour is greatest in the warm tropics and least at the cold poles.
How you could have got this
- If you were sure statement 1 is correct, (b) and (d) go: each of them leaves 1 out.
What you needed to know: Water vapour is concentrated near the surface and decreases with altitude.
- Then, if you were sure statement 2 is not correct, (c) goes: it includes 2.
What you needed to know: Water vapour is greatest in the warm tropics and least at the cold poles.
Only (a) is left. This one needs every statement.
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) Right: water vapour falls with height, but its share is not highest at the poles.
- (b) Wrong: the share is least, not greatest, at the poles.
- (c) Wrong: Statement 2 is incorrect.
- (d) Wrong: Statement 1 is correct.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2024, General Studies Paper I, Series A. The paper on upsc.gov.in.