# CIE AS & A Level Physics : 7.1 Progressive waves – Exam style question – Paper 1

### Question

Which statement about progressive waves is correct?

A    They are always transverse waves.

B    They can exist in solids but not liquids.

C    They decrease in frequency as their speed increases.

D    They transfer energy away from their source.

Ans:

### Question

Two balls float on the surface of the sea. The balls are separated by a distance of 1.30 m. A wave travels on the surface of the sea so that the balls move vertically up and down. The distance between a crest and an adjacent trough of the wave is 0.90 m. What is the phase difference between the two balls?
A 55o                 B 110o                     C 160o                    D 260o

Ans:

### Question

Two identical waves are produced by sources at points P and Q. The waves travel along different
paths to reach point R, as shown. Both waves have a wavelength of 6.0 cm. The waves are in phase at point R.
What is the phase difference between the waves as they leave points P and Q?
A  0°    B  60°    C 90°    D 120°

Ans:

### Question

A guitar string vibrates to create a sound. The speed of the wave in the guitar string is always
440 m $$s^{–1}$$. The vibrating string creates a sound wave that moves in the air with a speed of
330 m $$s^{–1}$$.
Which graph shows the variation of frequency f with the wavelength $$\lambda$$ for the waves in the string and in the air? ### Question

A wave of frequency 15Hz travels at 24 m s–1 through a medium.
What is the phase difference between two points 2.0 m apart?
A   There is no phase difference.
B   They are out of phase by a quarter of a cycle.
C   They are out of phase by half a cycle.
D   They are out of phase by 0.80 of a cycle.