Physics
Calculate the minimum distance in air required between the source of sound and the obstacle to hear an echo. Take speed of sound in air = 350 ms-1
Sound
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Answer
As we know,
Total distance travelled by the sound in going and then coming back = 2d
Given,
V = 350 ms-1
An important condition for hearing an echo is that the reflected sound should reach the ear only after a lapse of at least 0.1 s after the original sound dies off.
Hence, t = 0.1 s
Substituting the values in the formula above, we get,
Hence, the minimum distance in air required between the source of sound and the obstacle to hear an echo = 17.5 m
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