Question

A police car travels towards a stationary observer at a speed of 15 m/s. The siren on the car emits a sound of frequency 250 Hz. Calculate the recorded frequency. The speed of sound is 340 m/s.

Answer 1

Given : v_s = 15 m/s, n₀ = 250 Hz, v = 340 m/s 

To find : Frequency (n)

Formula : n = n₀(v/v - v_s)

Calculation : As the source approaches listener, apparent frequency is given by,