A siren is fitted on as car going towards a vertical wall at a speed of 36 km/h. A person standing on the ground, behind the car, listens to the siren sound coming directly from the source as well as that coming after refelction from the siren to the person and b. coming after reflection. Take the speed of sound to be `340ms^-1`

Explanation

The speed of the car is `36kmh^-1=0ms^1`.
a. Here the observer is at rest with respect to the medium and the source is going away from the observer. The apparent frequency heard by the observer is therefore,
v'=v/(v+u_s)v`
`=340/(340+10)+500Hz=486Hz.`
b. the frequency received by the wall is
`v''=u/(v-u_s)v=340/(340-10)xx500Hz=515Hz`
The wall reflects this sound without changing the frequency. Thus, the frequency of the reflected wave as heard by the ground observer is 515 Hz.