A source of sound and listener are approaching each other with a … - Vidyadip

MCQ

A source of sound and listener are approaching each other with a speed of $40 m/s.$ The apparent frequency of note produced by the source is $400 \,cps$. Then, its true frequency (in $cps$) is (velocity of sound in air $= 360 m/s$)

A
$420$
B
$360$
C
$400$
✓
$320$

✓

Answer

Correct option: D.

$320$

d
(d) $n' = n\,\left( {\frac{{v + {v_O}}}{{v - {v_S}}}} \right)\,n \Rightarrow 400 = n\,\left( {\frac{{360 + 40}}{{360 - 40}}} \right) \Rightarrow n = 320\,cps$

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