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UPSC Prelims 2013 · World Geography · Air, Winds and Climates
During a thunderstorm, the thunder in the skies is produced by the Select the correct answer using the codes given below.
- meeting of cumulonimbus clouds in the sky
- lightning that separates the nimbus clouds
- violent upward movement of air and water particles
- (a) 1 only
- (b) 2 and 3
- (c) 1 and 3
- (d) None of the above produces the thunder
Show the answer and explanation
Answer: (d) None of the above produces the thunder
Thunder is the shock wave from air heated to ~30,000 °C by lightning expanding suddenly — none of the listed causes.
Statement by statement
1. ✗ NO Clouds colliding don’t make thunder.
2. ✗ NO Lightning doesn’t “separate” clouds.
3. ✗ NO Updrafts build the storm but don’t make the sound.
The idea
A sound is a pressure disturbance travelling through a medium. Lightning heats a narrow channel of air almost instantly. The sudden expansion creates a shock wave heard as thunder. The cloud’s upward motion helps build the storm, but is different from the event that produces this sound.
Electrical charge builds in a storm → Lightning discharges → Air in the channel heats rapidly → Air expands suddenly → A pressure wave spreads outward → The observer hears thunder
The trap
All three sound like plausible storm physics.
Also know
Lightning is seen before thunder is heard because light travels much faster than sound. The time gap can roughly indicate distance: about three seconds corresponds to one kilometre under ordinary conditions. The rumble comes partly from different parts of the lightning channel reaching the listener at different times. Cumulonimbus can also produce hail and strong downdraughts.
🔒 Thunder = rapid expansion of lightning-heated air.
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