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A siren of frequency n approaches a stat...

A siren of frequency n approaches a stationary observer and then receedes from the observer. If the velocity of source `(V) lt lt ` the velocity of sound `(C )`, the apparent change in frequency is

A

`2nV//C`

B

`2nC//V`

C

`n//V`

D

`2VC//n`

Text Solution

Verified by Experts

The correct Answer is:
A
`n.=n((V)/(V-V_(S)))=n((C )/(C-V))`
`n..=n((C )/(C+V))`
`Deltan..=n.-n..=nC[(1)/(C-V)-(1)/(C+V)]`
`=nC[(2V)/(C^(2)-V^(2))]`
`V^(2)`can be neglected as `V lt lt C :. Deltan.=(2nV)/(C )`
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