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A policeman blows a whistle with a frequ...

A policeman blows a whistle with a frequency of 500 Hz.A car approaches him with a velocity of `15 ms^(-1)`.Calculate the change in frequency as heard by the driver of the car as he passes the policeman. Speed of sound in air is `300 ms^(-1)`.

A

25 Hz

B

50 Hz

C

100 Hz

D

150 Hz

Text Solution

Verified by Experts

The correct Answer is:
B
If the car approaches the policeman
`upsilon'=(v+v_(0))/(v-v_(s))xxupsilon=(300+15)/(300-0)xx500rArrupsilon'=525Hz`
If the car moves away from the policeman
`upsilon''=(v+v_(0))/(v-v_(s))xxupsilon=(300+15)/(300-0)xx500`
`upsilon''=475Hz`
Change in frequency=`upsilon'-upsilon''=525-475=50 Hz`
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