9702 AS Level Physics U14 Waves - Waves Basics Quiz

A sound wave moves with a speed of 320 m/s through air.
The variation with time of the displacement of an air particle due to this wave is shown in the graph.

Which statement about the sound wave is correct?

The graph shows the variation with time of displacement for two different waves X and Y.
Wave X has frequency f and amplitude A.
What is the frequency and what is the amplitude of wave Y?

A loudspeaker emits a sound wave into a tube initially full of water.
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?

Two loudspeakers are placed near to each other and facing in the same direction.
A microphone connected to an oscilloscope is moved along a line some distance away from the
loudspeakers, as shown.
Which statement about the waves emitted by the loudspeakers is not a necessary condition for
the microphone to detect a fixed point along the line where there is no sound?