Physics (AS & A Level) · May / June 2020 · Paper 13 · Question 27

A vertical tube is partially filled with water. A sound wave moves down the tube and is reflected by the surface of the water. The frequency of the sound wave is gradually increased from zero until a much louder sound is heard. [diagram of a vertical tube partially filled with water, with an arrow labelled 'sound' pointing down into the tube, 'tube' labelling the tube wall, and 'water' labelling the water] Water is then removed from the tube until a second louder sound is heard. Which diagram shows the new pattern of the stationary wave that is formed?

1. A[diagram A: tube with stationary wave pattern]
2. B[diagram B: tube with stationary wave pattern]
3. C[diagram C: tube with stationary wave pattern]
4. D[diagram D: tube with stationary wave pattern]

As printed in the paper