Question

Calculate the minimum distance at which a person should stand in front of a reflecting surface to
be able to hear an echo (speed of sound in air = 350 m/s).
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Answer 1

Explanation:

Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s) × 0.1 s = 34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance, that is, 17.2 m.