Two whistles A and B produces notes of frequencies 660 Hz and 596 Hz respectively. There is a listener at the mid-point of the line joining them. Now the whistle B and the listener start moving with speed 30 m/s away from the whistle A. If speed of sound be 330 m/s, how many beats will be heard by the listener

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Solution

The correct option is B
4

For observer note of B will not change due to zero relatice motion.

Observed frequency of sound produced by A

= $600 \frac{(330 - 30)}{330}$ = 600 Hz.

$∴$ No. of beats = 600 - 596 = 4

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