Physics
What should be the minimum distance between the source and reflector in water so that the echo is heard distinctly? (The speed of sound in water = 1400 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 = 1400 ms-1
As 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 between the source and reflector in water so that echo is heard distinctly = 70 m
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