Question

The siren on an emergency vehicle has a frequency of

840 Hz. The emergency vehicle passes you at a speed of

28 m/s .The frequency of the receding siren detected by you is?

Answer 1

The frequency of the receding siren detected by you is

$$f=\dfrac{c}{c+v}f_0=\dfrac{340}{340+28}840=776\text{ Hz}.$$