Physics (AS & A Level) · May / June 2016 · Paper 12 · Question 27

Sound waves of wavelength λ are emitted by a loudspeaker and pass through two slits P and Q. Two sound waves from the slits meet at R. [diagram showing loudspeaker, sound barrier with two slits P and Q, and microphone at R] What is the condition for an intensity maximum (loud sound) to be detected by a microphone at R?

1. AThe amplitudes of the two waves at R must be the same.
2. BThe distance PQ must be smaller than the wavelength λ.
3. CThe two waves from the slits must have travelled the same distance to R.
4. DThe two waves must be in phase at R.

As printed in the paper