Question

A siren is fitted on a car going towards a vertical wall at a speed of 36 Kmph. 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 reflection from the wall. Calculate the apparent frequency of the wave coming directly from the siren to the person.

Answer 1

Velocity of source = 36 Kmph 

V_S = 36 × \(\frac{5}{18}\) = 10 m/s 

Velocity of sound v = 340 m/s 

Frequency n = 500 Hz 

For the sound coming directly from the siren to the listener, source (siren) is moving away from the listener so 

V_S = -10 m/s V₂ = 0

Apparent frequency of the wave

= 485.7 Hz