Physics (AS & A Level) · Oct / Nov 2022 · Paper 13 · Question 23

An observer is standing on a railway platform. A train passes the observer at constant speed while emitting sound of constant frequency f from its whistle. What does the observer hear?

1. Asound of a decreasing frequency as the train approaches and of an increasing frequency as it moves away
2. Bsound of a higher frequency than f as the train approaches and of a lower frequency than f as the train moves away
3. Csound of a lower frequency than f as the train approaches and of a higher frequency than f as the train moves away
4. Dsound of an increasing frequency as the train approaches and as it moves away

As printed in the paper