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A siren emitting a sound of frequency 80...

A siren emitting a sound of frequency 800 Hz moves away from an observer towards a cliff at a speed of `15 ms^(-1)` Then, the frequency of sound that the observer hears in the echo reflected from the cliff is .......
(Take velocity of sound in air `= 330 ms^(-1))`

A

800 Hz

B

838 Hz

C

885 Hz

D

765 Hz

Text Solution

Verified by Experts

The correct Answer is:
B

We have `(f _(L))/( v + v _(L)) = (f _(S))/( v + v ._(S))`
`therefore (f _(L))/( 330 + 0) = (800)/( 330 - 15)`
`therefore f _(L) = 800 xx (330)/(315) = 838.1Hz`
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