Question

What frequency (in Hz) is received by a person watching an oncoming ambulance moving at 108 km/h and emitting a steady 900 Hz sound from its siren? The speed of sound on this day is 345 m/s.

Answer 1

Answer:985.71 Hz

Step-by-step explanation:

Given

Speed of ambulance (source)
`v_s=108\ kmph\approx 30\ m/s`

Original Frequency of sound wave
`f=900\ Hz`

speed of sound waves
`v=345\ m/s`

According to Doppler apparent frequency will be different to original frequency when speed of source is moving w.r.t to observer.

`f'=f((v+v_o)/(v-v_s))`

where f'=apparent frequency

f=original frequency

`v_o`=observer speed

`f'=900* ((345+0)/(345-30))`

`f'=900* ((345)/(315))`

`f'=985.71\ Hz`