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Question
The speed of sound in water is 1500 metres per second. How far away from an under-sea rock should a deep sea diver be so that he can hear his own echo ?
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Solution
We have to calculate the depth in water.
Given: Time taken to hear the echo t = 0.1 s
So time taken for sound to reach the reflecting surface
`(t_r) = 0.1/2` s
= `1/20` s
Speed of sound in water ν = 1,500 m/s
Therefore, distance of reflecting surface from the observer is
= `(v) xx (t_r)`
= `(1500) xx (1/20)` m
= 75 m
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