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A police car with a siren of frequency 8...

A police car with a siren of frequency `8 KHz` is moving with uniform velocity `36 Km//hr` towards a ball building which reflects the sound waves. The speed of sound in air is `320 m//s`. The frequency of the siren heard by the car driver is

A

`8.50 kHz`

B

`8.25 kHz`

C

`7.75 kHz`

D

`7.50 kHz`

Text Solution

Verified by Experts

The correct Answer is:
A

`f_("insident") = f_("reflected") = (320)/(320 - 10) xx 8 kHz`
`f_("observal") = (320 + 10)/(320) f_("reflected") = 8 xx (330)/(310) = 8.51 kHz approx 8.5 kHz`
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