Physics (AS & A Level) · May / June 2024 · Paper 12 · Question 23

A stationary sound wave is set up between a loudspeaker and a wall. A microphone is connected to a cathode-ray oscilloscope (CRO) and is moved along a line directly between the loudspeaker and the wall. The amplitude of the trace on the CRO rises to a maximum at a position X, falls to a minimum and then rises once again to a maximum at a position Y. The distance between X and Y is 33 cm. The speed of sound in air is 330 m s⁻¹. Which diagram could represent the CRO trace of the sound received at X?

1. Atime base 0.50 ms / cm
2. Btime base 0.50 ms / cm
3. Ctime base 0.50 ms / cm
4. Dtime base 0.50 ms / cm

As printed in the paper