Edexcel - London Examinations GCE, January 1999 - Paper 2 Question 4

4.

a) .

 

i) In a transverse vibration, the direction of vibration of the particles of the medium is at right angles to the direction of travel of the wave.

 

In a longitudinal wave, the direction of vibration of the medium is parallel to the direction of travel of the wave.

 iii)

ii) When the wire vibrates, it pushes and pulls on the air creating a series of compressions and rarefactions in the air, which together make up a longitudinal wave.

(7 marks)

 b)

i) Wave B is the one which was plucked vigorously as it produced a louder sound.

ii) Wave B is also associated with the loud sound as the amplitude is greater.

iii) Wave A shows the high-pitched sound, as the frequency is higher.

c) Let 'd' be depth,

 So, t = 0.2s

distance = 2 d (to fish and back = twice 'd)

v = 1 500 m/s

 v = d / t

so, d = v x t

or 2d = 1500 m/s x 0.2 s = 300m

 So

The returning pulse may last for some time as the fish are not all at exactly the same depth - some are at a bigger depth and so the sound takes longer to be reflected to the boat.

The second weak returning pulse is the sound reflected from the sea-bed which is deeper than the fish and hence takes a longer time to travel to the boat.