Physics (AS & A Level) · Feb / March 2021 · Paper 12 · Question 28

Two sources of microwaves P and Q produce coherent waves with a phase difference of 180°. The waves have the same wavelength λ. At the point S there is a minimum in the interference pattern produced by waves from the two sources. The distance (QS – PS) is called the path difference. Which expression could represent the path difference?

1. Aλ/4
2. Bλ/2
3. Cλ
4. D3λ/2

As printed in the paper