Two whistles A and B produces notes of frequencies 660 Hz and 596… - Vidyadip

MCQ

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
$2$
✓
$4$
C
$6$
D
$8$

✓

Answer

Correct option: 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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