Question

a source of sound of frequency 256 hz is moving rapidly towards a wall with velocity of 5 m/s .If the sound travels a speed of 330m/s then the number of beats heard by the observer who is standing between the wall and the source is

Answer 1

hope it helps comment if any doubt

Answer 2

Answer:  The number of beats heard by the observer is $4\ s^{-1}$.

Explanation:

Given that,

Frequency f = 256 hz

Velocity of source $v_{s}= 5 m/s$

Speed of sound v = 330 m/s

Using Doppler effect formula

$f' = \dfrac{v+v_{l}}{v+v_{0}}f$

Here, listener is not moving so, $v_{l}= 0$

$f' = \dfrac{330}{330+5}\times256$

$f' = 252.2 Hz$

The number of beats is

$n = f-f'$

$n = 256-252.2$

$n = 3.8\ s^{-1}$

$n = 4\ s^{-1}$

Hence, The number of beats heard by the observer is $4\ s^{-1}$.