A source of sound S has a frequency f. Wind is blowing from source to observer O with velocity u. If speed of sound with respect to air is C, the wavelength of sound detected by O is:
A
C+uf
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B
C−uf
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C
C(C+u)(C−u)f
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D
Cf
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Solution
The correct option is AC+uf Net velocity of sound with respect to ground. v′=vs+vm
Where vs is the velocity of sound with respect to medium and vm is the velocity of the medium.
Thus, v′=C+u
As both the source as well as the observer are at rest, so frequency will remain the same as f irrespective of the velocity of medium.
Let λ be the wavelength of the sound wave detected by observer.
Using, v′=f×λ C+u=fλ⇒λ=C+uf