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Two sound sources emitting sound each of...

Two sound sources emitting sound each of wavelength `lambda` are fixed at a given distance apart. A listener moves with a velocity `u` along the line joining the two sources. The number of beats heard by him per second is

A

`(2u)/(lambda)`

B

`(u)/(lambda)`

C

`sqrt(u lambda)`

D

`(u)/(2 lambda)`

Text Solution

Verified by Experts

The correct Answer is:
A

For first source
`n_(1) = n ((v - u)/(v)) = (1 - (u)/(v))n`
for Iind source
`n_(2) = n ((v + u)/(v)) = (1 + (n)/(v)) n`
Beat freq. `= [n_(1) - n_(2)] = n + (nu)/(v) - n + (nu)/(v)`
`= (2nu)/(v) = 2 (u)/(lambda) [:' v = n lambda :. (1)/(lambda) = (n)/(v)]`
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