The engine of a train moving with speed 10 m s⁻¹ towards a platform sounds a whistle at frequency 400 Hz. The frequency heard by a passenger inside the train is: (neglect air speed. Speed of sound in air = 330 m s⁻¹)
Options

Question

The engine of a train moving with speed 10 m s⁻¹ towards a platform sounds a whistle at frequency 400 Hz. The frequency heard by a passenger inside the train is: (neglect air speed. Speed of sound in air = 330 m s⁻¹)

Options

G1 Physics · Accepted Answer

The passenger and the horn are both fixed relative to the same train. Therefore there is no relative motion between source and observer inside the train, so the frequency heard by the passenger is the same as the emitted frequency. Thus, f(observed) = 400 Hz Hence option A follows.