Physics (AS & A Level) · Oct / Nov 2021 · Paper 12 · Question 29

Two waves, each with a constant amplitude, interfere and produce an interference pattern. The pattern has minima at fixed points where the displacement is zero at all times. Which statement describes the two waves?

1. AThey must be coherent and of the same amplitude.
2. BThey must be coherent but not necessarily of the same amplitude.
3. CThey must be of the same amplitude but not necessarily coherent.
4. DThey must not be coherent or of the same amplitude.

As printed in the paper