MCQ practice · SSC Physics Board questions · Chapter 7: Waves and Sound
The speed of sound in air:
- i. is proportional to the square of the temperature
- ii. does not depend on the pressure of the air
- iii. is inversely proportional to the square root of the density of the air
Think it through first, then pick an option.
- a i
- b ii
- c i and iii
- d ii and iii
Answer and explanation
Correct answer: d ii and iii
ii is true: a change of pressure does not change the speed. iii is true: v ∝ 1/√ρ. i fails: v ∝ √T.
Why the other options are wrong
- a i: i fails: the speed is proportional to the square root of the temperature. ii and iii are true, so i alone is not the answer.
- b ii: ii is true, but iii is true too (v ∝ 1/√ρ), so ii alone is not the full answer.
- c i and iii: i fails: the speed is proportional to the square root of the temperature. ii is true as well.
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