UPSC Prelims 2013 · GS Paper I
Question 72: Geography
During a thunderstorm, the thunder in the skies is produced by the
- 1.meeting of cumulonimbus clouds in the sky
- 2.lightning that separates the nimbus clouds
- 3.violent upward movement of air and water particles
Select the correct answer using the codes given below.
AnswerUPSC’s answer is (d).
Thunder is the sound of a shock wave. A lightning discharge heats the air along its path to several thousand degrees in a fraction of a second, so the air expands explosively and then contracts, producing the rumble. None of the three statements gives this cause: clouds do not meet to make a sound, lightning does not separate clouds, and the violent upward movement of air only builds up the charges that lead to lightning.
- 1. Clouds do not make thunder by meeting.
- 2. Lightning does not separate clouds; it heats air, which makes the sound.
- 3. Upward air movement builds charge but does not make thunder.
Why each option is right or wrong
- (a) Wrong. Cloud meeting does not make thunder.
- (b) Wrong. Neither lightning separating clouds nor upward air movement is the cause.
- (c) Wrong. Neither cloud meeting nor upward movement is the cause.
- (d) Correct. Thunder comes from the sudden heating and expansion of air by lightning, which none of the statements says.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.