Topic 3 - Wave Properties, Behaviours & Uses

Question 1

Four students and their teacher do an experiment to measure the speed of sound in air.
The teacher stands at a distance and fires a starting pistol into the air.
The students see the flash when the pistol is fired.
They measure the time from when they see the flash to when they hear the bang.
The students obtained a value of 240 m/s for the speed of sound.
The accepted value is 343 m/s.
Calculate the difference between the students’ value and the accepted value as a
percentage of the accepted value. (2)

Answer 1

343 - 240/343 x100 (1)
30% (1)

Question 2

Four students and their teacher do an experiment to measure the speed of sound in air.
The teacher stands at a distance and fires a starting pistol into the air.
The students see the flash when the pistol is fired.
They measure the time from when they see the flash to when they hear the bang.
When the distance was 100 m, the students measured the following times:
0.43 s 0.35 s 0.50 s 0.38 s
Explain why their times vary so much. (2)

Explain one way the students might improve this experiment. (2)

Answer 2

Reaction time is significant (1)
Reaction time will be different for each of the students (1)
Effects on reaction times (1)
Students are at different distances from starting pistol (1)
Anticipation of flash/bang (1)

Use a much longer distance/electronic timer (1)
Gives a more manageable time to measure/reduces/eliminates impact of reaction time (1)

Question 3

A radio station transmits on 97.4 MHz.
To receive the waves an aerial needs a length equal to half the wavelength of the radio
waves being transmitted.
Calculate the length of the aerial needed.
The speed of the radio waves is 3.00 × 108 m/s. (3)

Answer 3

Wavelength = wave speed/frequency (1)
3x10^8/97.4x10^6 (1)
1.5x10^8 (1)

Question 4

The speed of sound in air is 300 m/s.
The speed of sound in water is 1500 m/s.
Calculate the ratio of the speed of sound in air to the speed of sound in water. (2)

Answer 4

300:1500 (1)
1:5 (1)

Question 5

A water wave has a wavelength of 0.25 m and a frequency of 1.5 Hz.
Calculate the wave speed. (2)

Answer 5

0.25 x 1.5 (1)
0.38 (1)

Question 6

Sound waves are longitudinal waves.
Water waves are transverse waves.
Describe the difference between longitudinal waves and transverse waves. (3)

Answer 6

Longitudinal - vibrations parallel to direction of travel (1)
Transverse - vibrations perpendicular to direction of travel (1)
Connection between direction of travel with direction of vibration (1)

Question 7

Describe the motion of the particles for a loudspeaker as the wave travels through the air. (2)

Answer 7

Particles vibrate/oscillate backwards and forwards (1)
Along a radius/parallel to direction of travel/energy transfer (1)
About mean/fixed positions (1)

Question 8

A tank of water is used to study water waves.
QRS is a straight line
An earthquake starts at Q.
A seismic wave travels from Q to S.
The seismic wave is a longitudinal wave.
The frequency of the seismic wave is 12Hz.
A technician measured the frequency of the water wave by counting how many waves passed him in 15 s.
Explain why this would not be a suitable method for measuring the frequency of the seismic wave. (2)

Answer 8

Waves cannot be seen (on arrival) (1)
Person will need another way of detecting the waves (1)
As a person can’t count to 12 in 1 second/at a rate of 12 per second (1)
Frequency too high (1)

Question 9

A student is sitting on the shore of a lake watching ripples on the surface of the water moving past a toy boat.
The student has a stopwatch.
Describe how the student could determine the frequency of the ripples on the lake. (3)

Answer 9

Count the number of waves (1)
Arriving past a point in a specific time (1)
Use frequency = number of waves/time (1)

Question 10

The speed of light is 3.0 × 108 m/s.
The wavelength of yellow light is 5.8 × 10−7 m.
Calculate the frequency of yellow light. (3)
State the unit.
Use the equation: frequency = speed/wavelength

Answer 10

3 x 10^8/5.8 x 10^-7 (1)
5.2 x 10^14 (1)
Hz (1)

Question 11

Water waves are transverse waves.
Give another example of a transverse wave. (1)

Answer 11

Radio wave (1)
Microwave (1)
Infrared (1)
Visible light (1)
Ultraviolet (1)
X-rays (1)
Gamma rays (1)
EM-waves (1)
S-waves (1)

Question 12

A technician stands at the side of the tank.
He counts the peaks of the waves as they pass him.
12 peaks pass the technician in a time of 15 s.
Calculate the frequency of the wave. (2)

Answer 12

12/15 (1)
0.8 (1)

Question 13

Water waves are spreading out from a source.
A student measures the wavelength of the waves.
He uses a ruler to measure the distance from one crest to the next crest.
Explain how to improve the student’s method for measuring the wavelength. (2)

Answer 13

Measure across more than 1 wavelength (1)
Divide by the number of wavelengths (1)

Question 14

A sound wave in air travels a distance of 220 m in a time of 0.70 s.
State the equation linking speed, distance and time. (1)
Calculate the speed of the sound wave in air. (2)

Answer 14

Speed = distance/time (1)

220/0.7 (1)
310 (1)

Question 15

Sound travels slower in cold air than it does in warm air.
Speed of sound in air is =K/square root of density
The table gives some data about the speed of sound in air and the density of air.
Use the equation and the data in the table in Figure 10 to calculate the speed of sound in
warm air. (3)

Speed of sound in warm air = 331m/s density = 1.29
Speed of sound in cold air = ?m/s density = 1.16

Answer 15

K = 376 (1)
376/root of 1.16 (1)
349 m/s (1)

Question 16

A cork is floating on the water.
Describe the motion of the cork.
You should include how the cork moves relative to the direction of travel of the wave. (2)

Answer 16

Moves up and down (1)
Perpendicular to wave travel (1)

Question 17

A long metal rod is hit at one end by a hammer.
This causes a sound wave to travel along the inside of the metal rod.
Describe how hitting the rod causes a sound wave to travel along the inside of the rod. (2)

Answer 17

Particles at end vibrate more about fixed position (1)
Cause neighbouring particles to vibrate (1)

Question 18

To investigate refraction in a rectangular glass block a student uses: a light box, protracted and glass block.
Describe how the student should measure the angle of refraction. (2)

Answer 18

Mark/trace where the line went into and out of the glass block (1)
Join entry and exit points (1)
Use a protractor to measure the angle between the normal and refracted light ray (1)

Question 19

2 students, P and Q, try to measure the speed of sound in air. They are 50m apart.
P will clap his hands together.
When Q sees P clap his hands, she will start a timer.
When Q hears the clap, she will stop the timer.
Explain one way the students could improve their method. (2)

Answer 19

Make the distance between students larger/use microphone/data logger (1)
To give a more measurable time/to reduce effect of reaction times (1)

Question 20

radio waves from a transmitter move upwards,
then meet a boundary between lower and upper layers of the atmosphere.
Explain what happens to the radio waves after they meet the boundary between the lower
and upper layers.
Your explanation should refer to changes in direction and speed of the waves. (4)

Answer 20

Wave P refracts towards the normal (1)
Because P slows down (1)
Wave Q is reflected at an equal angle to the boundary (1)
Without change of speed of Q (1)

Question 21

When white light crosses the boundary between air and glass, it can split up into the colours of the spectrum.
Explain, in terms of speed, why the light behaves like this. (3)

Answer 21

The colours have different wavelengths (1)
Different wavelengths/colours travel at different speeds (1)
So refract by different amounts (1)

Question 22

When the prongs of a tuning fork are struck, the prongs vibrate forwards and backwards/left and right.
Describe how the vibrating tuning fork causes a sound wave to travel through the air. (2)

Answer 22

The prong makes the air vibrate/oscillate (1)
In the same direction as the air travels (1)

Question 23

Which colour of visible light has the longest wavelength? (1)

Answer 23

Red

Question 24

Explain refraction and total internal reflection (6)

Answer 24

Refraction:
• Angle of incidence marked
• Angle of refraction marked
• Angles are measured from the normal
• Angle of refraction is bigger than the angle of incidence
• Rays of light travel in straight lines
• Refraction occurs at a boundary between two materials of different (optical) density
• The angle of incidence is less than the angle of refraction when light passes into a less dense medium (glass into air)
• Refraction is a change in direction of a light ray.
• Refracted rays bend away from the normal when light passes into a less dense medium (glass into air)
• The ray in the more dense medium (glass) travels more slowly

Total Internal Reflection:
• Possible critical angle marked
• Light stays inside the glass
• Only occurs when the incident light is in the more dense medium
• Only occurs when the incident angle is equal to greater than the critical angle
• Critical angle for glass is about 42’
• Angle of incidence is equal to the angle of reflection

Question 25

A transducer can transmit and detect ultrasonic waves.
Ultrasonic waves are transmitted by a transducer on the bottom of a ship.
The waves reflect off the sea floor and are received back at the transducer.
The waves travel at 1500 m / s.
The time between transmission and reception is 48 milliseconds.
Calculate the depth of the water. (2)

Answer 25

1/2 x v x t = 1/2 x 1500 x 0.048 (1)
36 (m) (1)

Question 26

Describe the difference between ‘infrasound’ and ‘ultrasound’. (2)

Answer 26

Infrasound is less than 20Hz (1)
Ultrasound is more than 20,000Hz (1)

Question 27

Explain how vibrations from earthquakes may be used to study the core of the Earth. (4)

Answer 27

Use of seismometers (1)
Waves can be refracted in the interior of the earth (1)
Sowing different densities (1)
Some seismic waves are transverse and some are longitudinal (1)
S-wave/transverse waves shadow zone shows part of the earth must be liquid (1)
P-wave/longitudinal waves can go through the core/liquid (1)
Mention of S and P waves (1)

Question 28

Which of these is a frequency of ultrasound? (1)

A 2.3 Hz
B 23 Hz
C 2.3 kHz
D 23 kHz

Answer 28

23 kHz

Question 29

The frequency of the seismic wave is 12 Hz.
The wave speed of the seismic wave is 7 km / s.
Calculate the wavelength of the seismic wave, in metres. (3)
Use the equation:
Wavelength = wave speed/frequency

Answer 29

7 km/s = 7 m/s (1)
7 x 10^3/12 (1)
580 (1)

Question 30

Ultrasound has many uses.
One device called a pest repeller emits ultrasound.
The ultrasound keeps mice out of the garden.
Explain why the device affects mice but does not affect humans. (2)

Answer 30

Frequency (1)
Is in mouse hearing range but not in human hearing range (1)

Question 31

A technician has an ultrasound device.
This device can emit and detect short pulses of ultrasound.
The device can also measure the time, in ms, from emitting a pulse to detecting the same
pulse.
Describe how the technician can use this device to determine the speed of ultrasound in air. (3)

Answer 31

Send pulse to a wall/reflecting surface/detect the echo (1)
Measure distance (to wall and time to echo) (1)
Use speed = 2 x distance/time (1)

Question 32

Sonar is an example of a use of ultrasound.
State one other example of a use of ultrasound. (1)

Answer 32

Studying the earth’s structure

Question 33

State an example of a use of infrasound. (1)

Answer 33

Foetal scanning

Question 34

Are P-waves transverse or longitudinal? (1)
Can P-waves be refracted? (1)

Answer 34

Longitudinal (1)
Yes they can be refracted (1)

Question 35

Explain why it is difficult to predict when an earthquake will happen. (2)

Answer 35

The release of energy/pressure in the earth’s surface (1)
Too difficult to measure/work out when this release of energy will happen (1)

Question 36

At seismic stations, scientists record the arrival of earthquake waves.
They use this data to locate where an earthquake happened.
Describe how they use the data to find out where an earthquake happened. (6)

Answer 36

Data collection:
• S and P arrival times found
• Use or collect data from more than one station
Manipulation / Calculation for one station
• Circle drawn on map with station at centre
• Circle drawn on map at appropriate distance from station
• Earthquake on that circle
• (Distance found from) S minus P time

Triangulation:
• Repeat calculation / drawing with at least three stations
• Epicentre / earthquake at point of intersection of all three (or more) circles
• Triangulation
• Meaning of triangulation

Question 37

On reason for the mantle being hotter near the core is that (1)

A the Earth’s crust is a solid
B the Earth’s core is a liquid
C the Earth is radiating heat to space
D the Earth is absorbing heat from space

Explain how this temperature difference causes the tectonic plates in the Earth’s crust to move. (2)

Answer 37

the Earth is radiating heat to space (1)

Hot material rises/cold material falls (1)
Causes material under the plate to move sideways (1)
Because of uneven heating (1)

Question 38

All earthquakes emit S-waves and P-waves.
Scientists determine the position of earthquakes by detecting these seismic waves.
The S-waves and P-waves do not always travel in straight lines.
Explain why the S-waves and P-waves do not always travel in straight lines. (2)

Answer 38

Change in wave speed (1)
With change in density/state of material/rock (1)

Question 39

S-waves and P-waves travel at different speeds.
The scientists use the (S–P) time to estimate how far away the earthquake is.
Suggest what is meant by (S–P) time. (2)

Answer 39

The time difference (1)
Of P and S waves arriving/being recorded/detected (1)

Question 40

A specific electromagnetic wave has a frequency greater than visible light.
The wavelength of this wave is longer than that of X-rays.
This electromagnetic wave is (1)

A a gamma wave
B an infrared wave
C a microwave
D an ultraviolet wave

Answer 40

an ultraviolet wave

Question 41

A woman is checking that a banknote is genuine.
She is using a lamp which emits a radiation which is part of the electromagnetic spectrum.
Explain how two different electromagnetic radiations enable the woman to check the banknote. (2)

Answer 41

Ultraviolet lamp absorbed by fluorescent substance/bank note (1)
Which emits visible light (into eye) (1)

Question 42

A light wave from a star has a frequency of 6.67 × 1014 Hz and a wavelength of 4.50 × 10−7 m.
The star is 4.00 × 1016 m away from Earth.
Calculate the time it takes light from the star to reach the Earth. (3)

Answer 42

Speed = 6.67 × 10^14 x 4.5 x 10^-7 (1)
4 × 10^16/6.67x10^14 x 4.50 × 10^−7 (1)
1.33 x 10^8 (1)

Question 43

Explain the differences between longitudinal and transverse waves.
Your explanation should refer to ultraviolet, ultrasound and seismic waves. (6)

Answer 43

• Longitudinal {vibrations/oscillations} are {along/parallel to/in the same direction as} the direction of {travel/energy transfer}
• Transverse {vibrations/oscillations} are {across/perpendicular to/90° to/right angles to} the direction of {travel/energy transfer}
• Ultraviolet waves are transverse
• Ultrasound waves are longitudinal (ignore sound - not on list)
• Some seismic waves are longitudinal and some are transverse
• P waves are longitudinal
• S waves are transverse
• Longitudinal waves need a material for the vibrations whereas electromagnetic waves can pass through a vacuum

Question 44

A man uses a dog whistle to call his dog.
The whistle uses ultrasound.
The dog can hear the whistle but the man cannot.
Explain why the dog can hear the whistle but the man cannot hear the whistle. (2)

Answer 44

Frequency/Hz (1)
Above 20,000 (1)

Question 45

A dog is 140 m away from a man.
The ultrasound (dog whistle) takes 0.42 s to travel from the man to the dog.
Calculate the speed of ultrasound.
State the unit.
(3)

Answer 45

140/0.42 (1)
330 (1)
m/s (1)

Question 46

An earthquake P-wave has a frequency of 15 Hz.
The earthquake P-wave is (1)

A an infrasound wave
B an ultrasound wave
C an electromagnetic wave
D a transverse wave

Answer 46

an infrasound wave

Question 47

Earthquakes occur when two tectonic plates move against each other.
Explain what causes the tectonic plates to move. (2)

Answer 47

Convection currents (1)
In mantle (1)