Physics (AS & A Level) · Oct / Nov 2019 · Paper 11 · Question 23

Source S emits microwaves with a constant amplitude. The microwaves hit a metal screen P and are reflected. A stationary wave is formed between S and P. The wavelength of the microwaves is much smaller than the distance between S and P. A detector Q is moved at a slow, constant speed from S to P. What happens to the amplitude of the signal detected by Q?

1. Adecreases steadily
2. Bincreases and decreases regularly
3. Cincreases steadily
4. Dremains constant

As printed in the paper