What is the minimum distance from a reflecting surface required for a person to hear a distinct echo, given that the speed of sound in air is 340 m/s and the human ear can distinguish two sounds separated by at least 0.1 s?

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Question

What is the minimum distance from a reflecting surface required for a person to hear a distinct echo, given that the speed of sound in air is 340 m/s and the human ear can distinguish two sounds separated by at least 0.1 s?

Accepted Answer

17 m — The sound must travel to the wall and back, so the total distance is 2d. Using d = v × t / 2 = 340 × 0.1 / 2 = 17 m. Option A incorrectly uses the full distance without halving. Option C doubles the answer unnecessarily. Option D uses an incorrect time value of 0.01 s.

Answer

34 m

Answer

17 m

Answer

68 m

Answer

3.4 m

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