UPSC Prelims 2006 · General Studies

Question 4: Science and Technology

In which one among the following is the speed of sound maximum?

aAir at 0 °C

bAir at 100 °C

cWater

dWood

AnswerThe answer is (d).

Sound travels fastest in solids, slower in liquids and slowest in gases, because a denser, stiffer medium hands the vibration on faster. Roughly: air is about 330 m/s at 0 degrees C and about 385 m/s at 100 degrees C, water about 1,500 m/s, and wood several thousand metres per second (it varies with the wood and the grain). Warm air carries sound faster than cold air, but still far slower than any liquid or solid.

Why each option is right or wrong

(a) About 330 m/s; gases are the slowest medium.
(b) Faster than at 0 degrees C because speed rises with temperature, but still a gas and far below water.
(c) About 1,500 m/s; liquids are faster than gases but slower than solids.
(d) Wood, a solid, carries sound at several thousand m/s, the highest of the four.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2006, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.