A whistle sends out 256 waves in a second. If the whistle approaches the observer with velocity $1/3$ of the velocity of sound in air, the number of waves per second the observer will receive

Question

Dr. Abubacker · Accepted Answer

(a) Wave number $= \frac{1}{\lambda}$ but $\frac{1}{\lambda^{'}} = \frac{1}{\lambda}\left( \frac{v}{v - v_{s}} ight)$ and $v_{s} = \frac{v}{3}$
$	herefore(W.N.)^{'} = (W.N.)\left( \frac{v}{v - v/3} ight) = 256 	imes \frac{v}{2v/3}$
$= \frac{3}{2} 	imes 256 = 384$

Q. A whistle sends out 256 waves in a second. If the whistle approaches the observer with velocity $1/3$ of the velocity of sound in air, the number of waves per second the observer will receive

Explanation

Reviewed by Dr. Abubacker

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