A boy is walking away from a wall towards an observer at a speed of $1\ metre/sec$ and blows a whistle whose frequency is $680\ Hz.$ The number of beats heard by the observer per second is (Velocity of sound in air $= 340\ metres/sec$)

Question

Dr. Abubacker · Accepted Answer

(d) Observer hers two frequencies
(i) $n_{1}$ which is coming from the source directly
(ii) $n_{2}$ which is coming from the reflection image of source
So, $n_{1} = 680\left( \frac{340}{340 - 1} \right)$ and $n_{2} = 680\left( \frac{340}{340 + 1} \right)$
$\Rightarrow n_{1} - n_{2} = 4\ beats$

Q. A boy is walking away from a wall towards an observer at a speed of $1\ metre/sec$ and blows a whistle whose frequency is $680\ Hz.$ The number of beats heard by the observer per second is (Velocity of sound in air $= 340\ metres/sec$)

Explanation

Reviewed by Dr. Abubacker

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