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प्रश्न
A sound made on the surface of a lake takes 3 s to reach a boatman. How much time will it take to reach a diver inside the water at the same depth?
Velocity of sound in air = 330 ms−1
Velocity of sound in water = 1450 ms−1
उत्तर
∵ s = `"d"/"t"`
⇒ 330 = `"d"/3`
⇒ d = 990 m
Now for the diver inside water
s = `"d"/"t"`
t = `990/(1,450)`
∴ t = 0.682 sec.
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