Question

If the siren is at rest and the observe is moving away from the siren at 30 m/s then present frequency does the observe hear __________(Hz).

(velocity of sound V=330 m/s and frequency as 22 Hz)If the siren is at rest and the observe is moving away from the siren at 30 m/s then present frequency does the observe hear __________(Hz).

(velocity of sound V=330 m/s and frequency as 22 Hz)

Answer 1

Given that,

Speed of observer = 30 m/s

Frequency of sound = 22 Hz

Speed of sound = 330 m/s

If the siren is at rest.

Then the speed of source is zero.

We need to calculate the frequency of sound that the observer hears

Using formula of apparent frequency

$f'=\dfrac{v+ v_{0}}{v- v_{s}}\times f$

Where, v = speed of sound

$v_{o}$ = speed of observer

$v_{s}$ = speed of source

f = frequency

Put the value into the formula

$f'=\dfrac{330+30}{330-0}\times22$

$f'=24\ Hz$

Hence, The frequency of sound that the observer hears is 24 Hz.