UPSC Prelims 2002 · General Studies
Question 9: Geography
Consider the following climatic and geographical phenomena:
- 1.Condensation
- 2.High temperature and humidity
- 3.Orography
- 4.Vertical wind Thunder-cloud development is due to which of these phenomena?
AnswerThe answer is (d).
A thunder-cloud (cumulonimbus) forms where warm, moist air is forced up violently. High temperature and humidity give unstable, moisture-laden air; orography (hills) can force it upward; vertical winds carry it to great heights; and condensation releases latent heat that keeps the air rising. All four therefore contribute to its development.
- 1. Condensation releases latent heat that keeps the air rising.
- 2. High temperature and humidity give unstable, moist air.
- 3. Hills force air up and can start the cloud growing.
- 4. Strong vertical air currents build the cloud to great heights.
How you could have got this
- If you were sure statement 1 is correct, (b) goes: it leaves 1 out.
What you needed to know: Condensation releases latent heat that keeps the air rising.
- Then, if you were sure statement 2 is correct, (c) goes: it leaves 2 out.
What you needed to know: High temperature and humidity give unstable, moist air.
- Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.
What you needed to know: Hills force air up and can start the cloud growing.
Only (d) is left. You didn’t need statement 4.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
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) Leaves out orography and vertical winds, which also lift the air.
- (b) Leaves out condensation, whose latent heat feeds the updraught.
- (c) Leaves out high temperature and humidity, the source of unstable moist air.
- (d) Right: all four phenomena contribute.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2002, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.