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Two sources A and B are sounding notes of frequency 680 Hz. A listener moves from A to B with a constant velocity u. If the speed of sound is 340 m/s, What must be the value of u so that he hears 10 beats per second?

A

`2.0(m)/(s)`

B

`2.5(m)/(s)`

C

`30(m)/(s)`

D

`3.5(m)/(s)`

Text Solution

Verified by Experts

The correct Answer is:
B

Apparent frequency due to source A is
`n'=(v-u)/(v)xxn`
Apparent frequency due to source B is
`n''=(v+u)/(v)xxn`
`n''-n'=(2u)/(v)xxn=10`
`u=(10v)/(2n)=(10xx340)/(2xx680)=2.5(m)/(s)`
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