Question

The engine of a train sounds a whistle at frequency v. The frequency heard by a passenger is
(a) > v
(b) < v
(c) =1v
(d) =v

Answer 1

The engine of a train sounds a whistle at frequency v. The frequency heard by a passenger is v

Explanation:

Since the source and the observer travel both at the same velocity there is no relative motion. Therefore there is no Doppler effect and no visible frequency shift.

Doppler effect: As wave energy travels from two objects, Unlike Waves of Sound or Radio, If one or both are moving, The wavelength might seem different. This is known as the Doppler effect.