First slide

Doppler

Question

A source of sound of frequency 256 Hz is moving towards a wall with a velocity of 5 m/s. Velocity of sound is 330 m/s. The number of beats heard by an observer standing behind the source is nearly

Moderate

A

$256 [\frac{330}{325} - 1]$
B

$256 [1 - \frac{330}{325}]$
C

$256 [\frac{330}{325} - \frac{330}{335}]$
D

$256 [\frac{330}{325} - \frac{330}{325}]$

Solution

The observer hears a direct sound. In this case, the source is moving away from the observer' The apparent frequency Y n' is given by
$n^{'} = n [\frac{v}{v + v_{s}}] = 256 [\frac{330}{330 + 5}] = 256 [\frac{330}{335}] The observer also hears the reflected sound' In this case, the echo source is moving to wards the stationary observer . The apparent hequency n' is given by n^{''} = n [\frac{V}{V - V_{s}}] = 256 [\frac{330}{330 - 5}] = 256 [\frac{330}{325}] ∴ Beat frequency = n^{''} - n^{'} = 256 [\frac{330}{325} - \frac{330}{335}]$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App