Physics (AS & A Level) · Oct / Nov 2017 · Paper 11 · Question 23

A loudspeaker emits a sound wave into a tube initially full of water. [diagram of loudspeaker, tube, water, tap with lengths x and y] A tap at the bottom of the tube is opened so that water slowly leaves the tube. For some lengths of the air column in the tube, the sound heard is much louder. The first loud sound is heard when the air column in the tube has length x. The next time that a loud sound is heard is when the air column in the tube has length y. What is the wavelength of the sound wave from the loudspeaker?

1. A2x
2. B4y
3. C2(y – x)
4. D4(y – x)

As printed in the paper