Waves

Question 1

(1) Which of these best describes what is transferred by the water wave?

Answer 1

energy only

Question 2

(2) The wavelength of the wave is 0.8 m.

Calculate the distance between the floats.

Answer 2

(number of waves =) 7 (1)
(distance between floats =)7 × 0.8
(1)

Question 3

(1) The frequency of the wave is 0.4 Hz.

How many complete wavelengths pass each float in 20 s?

Answer 3

8

Question 4

(1) Suggest one piece of information the man could gain about the boat by
observing the wave that made it.

Answer 4

size (1)
• mass (1)
• speed (1)
• direction of travel (1)

Question 5

(3) The wave reaches shallow water before it reaches the shore.
Water waves travel more slowly in shallow water.
Draw a diagram to show how the wave travels in the shallow water.

Answer 5

change of direction (1)
• towards the normal (1)
• λ shorter than in deep water
(1)

Question 6

(3) Some microwaves have a frequency of 1.5 × 1010 Hz.
They travel at a speed of 3.0 × 108
m/s.
Calculate their wavelength.

Answer 6

substitution: (1)
3.0 × 108
=1.5 × 1010 × λ
transposition: (1)
λ = c/f or
(λ =)3.0 × 108

1. 5 × 1010
   evaluation: (1)
2. 02 (m)

Question 7

(3) A student suggested that the time between the arrival of the P-wave and the
S-wave was proportional to the distance of the station from the earthquake.
Use the charts to evaluate whether this is correct or not.

Answer 7

• (a)statement about either
distance travelled or arrival
times of any two waves (1)
• (b)statement comparing any
pair of S-P times (1)
• correct comparison between
(a) and(b)leading to a
conclusion (1)

Question 8

(1) seismic waves are…infrasound waves are…

Answer 8

longitudinal and transverse, longitudinal only

Question 9

(1) State what happens to a P-wave when it crosses from the mantle into the core

Answer 9

(sudden) decrease in speed

Question 10

(2) Describe how the speed of a P-wave changes between a depth of 1000 km
and 2500 km.

Answer 10

the (speed) increases (1)
with any one of
• as depth increases (1)
• linearly (1)
• from 11.8 to 14 (km/s) (1)
• by 2.2

Question 11

(3) The average speed of a P-wave in the mantle is 12 km/s.
A P-wave travels vertically down from the surface and reflects from the
core–mantle boundary back to the surface.
It travels a total distance of 5800 km.
Calculate the total time of travel for the wave

Answer 11

substitution (1)
 12 = 5800 ÷ t
transposition (1)
t = 5800 ÷ 12
evaluation (1)
480 (s)

Question 12

(1) The diagram represents water waves travelling from deep water into an area of
much shallower water
State the name of the effect shown in this diagram

Answer 12

refraction

Question 13

(1) When the waves go from deep water to shallow water, the

Answer 13

wavelength decreases

Question 14

(2) Explain another change which can be seen from the diagram when the waves
go from deep water to shallow water.

Answer 14

change in direction (1)
• towards the normal (1)
• (resulting from ) decrease
in speed (1)
• (because) the left hand
part of the wavefront {hits
the boundary first / slows
down first} (1)

Question 15

(3) The velocity of the waves in deep water is 25 m/s.
The wavelength is 120 m.
Calculate the frequency of the waves

Answer 15

substitution (1)
25 = 120 x f
transposition (1)
f = 25/120
evaluation (1)
0.21 (Hz)

Question 16

(3) Explain the difference between transverse and longitudinal waves

Answer 16

light waves are transverse
waves / sound waves are
longitudinal (1)
• in transverse waves
oscillations are at right
angle to the direction of
travel (1)
• in longitudinal waves
oscillations are parallel to
the direction of travel (1)

Question 17

(2) Describe how the air particles move when a sound wave passes.

Answer 17

(Particles) vibrate/oscillate
(1)
• (vibration) parallel to
direction of wave /
propagation (1)

Question 18

(1) 20 waves are sent out in 4 seconds.

The frequency of the wave is

Answer 18

5 Hz

Question 19

(2) S waves are one type of seismic wave. They travel at 0.65 km/s.
There is a seismometer 80 km away from point E.
Show that it takes about 2 minutes for the S waves from the earthquake to
reach the seismometer.

Answer 19

substitution (1)
0.65 = 80 / t
transposition (1)
t = 80 / 0.65
(123 seconds)

Question 20

(3) Describe how scientists can use seismometer records of P and S waves to
locate the epicentre.

Answer 20

detection of arrival of P and S
waves (1)
measurement of difference in
arrival times (1)
calculation of distance (from
epicentre to station) (1)
triangulation/using three /
several stations (1)