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
A$2$
B$4$
C$6$
D$8$
Medium
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B$4$
b (b) For observer note of $B$ will not change due to zero relative motion.
Observed frequency of sound produced by $A$
= $660\frac{{(330 - 30)}}{{330}} = 600\,Hz$
$\therefore $ No. of beats $= 600 -596 = 4$
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