Physics (AS & A Level) · Oct / Nov 2018 · Paper 12 · Question 29

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. In the expressions shown, n is an integer. Which expression represents the path difference?

1. Anλ
2. B½ nλ
3. C(n + ½)λ
4. D(2n + ½)λ

As printed in the paper