Physics (AS & A Level) · Feb / March 2023 · Paper 12 · Question 22

An observer hears a sound wave emitted from a moving source. The observed frequency is less than the frequency of sound emitted from the source. What could be the reason for this?

1. AThe source is moving away from the observer.
2. BThe source is moving towards the observer.
3. CThe speed of the sound wave in air decreases due to the movement of the source.
4. DThe speed of the sound wave in air increases due to the movement of the source.

As printed in the paper