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StudyPacks
STUDY.
KS4
SCIENCE
Electromagnetic Waves
Uses and Dangers
This Study Pack aims to cover:
1. The uses and dangers of Electromagnetic waves.
.
SP11
Study Packs are prepared by Qualified Teachers and Specialists and are a complete range of comprehensive
compiled resources based on the UK National Curriculum covering the Primary and Secondary Frameworks
including SATs and GCSE examinations.
Student Name
Contents
Electromagnetic Waves
2-13
Practice questions
14-17
Exam questions
18-28
Mark scheme
29-32
1
2
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The electromagnetic spectrum Notes
The electromagnetic spectrum is a continuous range of wavelengths. The types of radiation that occur
in different parts of the spectrum have different uses and dangers, which depend on their wavelength
and frequency.
Refraction from a prism
White light can be split up using a prism to form a spectrum. The light waves are refracted as they
enter and leave the prism. The shorter the wavelength of the light, the more it is refracted. As a result,
red light is refracted the least and violet light is refracted the most, causing the coloured light to
spread out to form a spectrum.
Visible light is just one type of electromagnetic radiation. There are various types of electromagnetic
radiation, some with longer wavelengths than visible light and some with shorter wavelengths
than visible light.
The electromagnetic spectrum
Electromagnetic waves form a continuous spectrum. You should know the order of electromagnetic
waves in the spectrum as shown in the table below.
The main types of electromagnetic radiation
4
energy
frequency
wavelength
type of electromagnetic radiation
typical use
lowest
lowest
longest
radio waves
television signals
microwaves
cooking, mobile phones
infrared
optical fibre communication
visible light
seeing
ultraviolet
detecting forged bank notes
X-rays
medical images of bones
gamma radiation
killing cancer cells
highest
highest
shortest
Radio waves have the lowest frequencies and longest wavelengths, while gamma waves have highest
frequencies and shortest wavelengths.
The wavelengths vary across the electromagnetic spectrum from about 10–15 m to more than 104 m.
Communicating with waves: radio waves and microwaves
Radio waves, microwaves, visible light and infrared can all be used for communication. You should
know some typical examples of these, and associated hazards.
Radio waves
Radio waves are used to transmit television and radio programmes. Television uses higher frequencies
than radio.
A radio programme receiver does not need to be directly in view of the transmitter to receive
programme signals. Diffraction allows low-frequency radio waves to be received behind hills, although
repeater stations are often used to improve the quality of the signals.
The lowest frequency radio waves are also reflected from an electrically charged layer of the upper
atmosphere, called the ionosphere. This means that they can still reach receivers that are not in the
line of sight because of the curvature of the Earth's surface.
Microwaves and
radio waves in the
atmosphere
5
Microwaves
A mobile phone mast - an example of a microwave transmitter
Microwave radiation can also be used to transmit signals such as mobile phone calls.
Microwave transmitters and receivers on buildings and masts communicate with the
mobile telephones in their range. Some people think that mobile phones, which
transmit and receive microwaves, may be a health risk. This is not accepted by
everyone, as the intensity of the microwaves is too low to damage tissues by heating, and microwaves
are not ionising.
Certain microwave radiation wavelengths pass through the Earth's atmosphere and can be used to
transmit information to and from satellites in orbit. Satellite television signals use microwaves
Communicating with waves: visible light and infrared
Radio waves, microwaves, visible light and infrared can all be used for communication. You should
know some typical examples of these, and associated hazards.
Visible light
Visible light is the light we can see. It allows us to communicate with one another through books, hand
signals and video, for example. The use of visible light needs the transmitter and receiver to be in the
line of sight. But it is more secure against eavesdroppers than radio waves.
Cameras let us record still pictures and movies, and photography is an important use of visible light.
Very bright light can damage our eyes – you should never look directly into the Sun.
Infrared
Optical fibres
We cannot see infrared radiation, but we can feel it as heat energy. High intensity infrared is used in
heaters, toasters and grills, and it can cause burns. Infrared sensors can detect heat from the body.
They are used in:

security lights

burglar alarms.
Infrared radiation is also used to transmit information from place to place, including:

remote controls for television sets and DVD players

data links between computers.
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13
ELECTROMAGNETIC WAVES
Name of wave Uses
Dangers
Radio wave
Microwave
Infrared waves
Light waves
Ultraviolet waves
x-rays
Gamma
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Communicate - stay in touch
Aims
Electromagnetic waves are all around us. They are how we communicate over short and long distances.
After completing this worksheet, you should know the order of the parts of the spectrum, some of their
properties and how microwaves and radio waves interact with the ionosphere.
Questions
1.The table below shows some parts of the electromagnetic spectrum drawn by a student. The parts of
the spectrum and values of the wavelengths are placed in the wrong order.
Short
wavelength
Long
wavelength
microwaves
radio
waves
ultraviolet
infrared
gamma
rays
X-rays
visible
103 m
10-14 m
10-10 m
10-8 m
10-2 m
10-6 m
10-5 m
a)In the table below, place the parts of the electromagnetic spectrum in the correct order. Give the
correct wavelengths in the boxes below.
Remember 10-14 is smaller than 10-10.
Small
wavelength
Long
wavelength
radio waves
103 m
Bi) Every part of the electromagnetic spectrum travels at a speed of 3.0 x 108 m/s in a
vacuum.
Name two other properties common to all electromagnetic waves.
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
ii State which type of electromagnetic wave has the highest energy.
…………………………………………………………………………………………………
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iii Radio waves have longer wavelengths than microwaves. Rearrange the following formula
and use the numbers in your answer to part a above to show that microwaves have a higher
frequency than radio waves.
wave speed = frequency  wavelength
…………………………………………………………………………………………………
…………………………………………………………………………………………………
…………………………………………………………………………………………………
2.The table gives information about some radio waves and microwaves. The ionosphere is a layer of
the Earth’s atmosphere which changes constantly in its ability to reflect some radio waves.
Wave name
Frequency range
Effect of ionosphere
microwaves
above 3000 MHz
passes through
ultra-high frequency radio (UHF)
300 – 3000 MHz
passes through
very high frequency radio (VHF)
30 – 300 MHz
reflects
high frequency radio (HF)
2 – 30 MHz
reflects
a On the diagram show,
what happens to the HF radio wave as it hits the ionosphere.
the position of a satellite used to transmit t.v. pictures to Earth.
a microwave travelling from the satellite to the Earth.
b)Use the table to decide what frequencies can be used to send a signal to the satellite.
…………………………………………………………………………………………………………
c)Explain how it is possible to use HF radio to talk to someone on the other side of the Earth.
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…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
d)You are listening to an HF radio programme from another country. Suddenly the signal fades.
Explain why this may have happened.
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
e)Infrared radiation emitted by the surface does not escape from the Earth. It is absorbed by the
atmosphere. Explain the difference between absorption and reflection.
……………………………………………………………………………………………………
……………………………………………………………………………………………………
f)Where are microwaves used around the home for communication?
……………………………………………………………………………………………………
……………………………………………………………………………………………………
Discussion
The ozone layer is another layer in the atmosphere. It absorbs some of the Sun’s ultraviolet radiation. The
ozone layer started to decrease in size some years ago.
What might happen if this continues?
Some people confuse the loss of the ozone layer with greenhouse warming. What is the difference?
17
Exam Questions
Q1.
The diagram below shows the range of wavelengths and frequencies for all the types of
radiation in the electromagnetic spectrum.
X‑rays, which have frequencies in the range 1018–1021 Hz are already marked on the diagram.
Complete the diagram by adding the following:
(a)
gamma radiation, which has shorter wavelengths than X‑rays;
(b)
radio waves which have wavelengths longer than 0.1m;
(c)
the visible spectrum which has wavelengths from 400 nm (violet) to 700 nm (red);
(d)
ultraviolet radiation (i.e. radiation with a higher frequency than violet light);
(e)
microwaves which have a shorter wavelength than radio waves and infrared radiation
which has a higher frequency than microwaves;
(f)
an FM radio programme on 92MHz. (Show this with an arrow )
(Total 7 marks)
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Q2.
Radio waves, ultra-violet, visible light and X-rays are all types of electromagnetic radiation.
(a)
Choose wavelengths from the list below to complete the table.
3 × 10–8 m 1 × 10–11 m
TYPE OF RADIATION
5 × 10–7 m
1500 m
WAVELENGTH (m)
Radio waves
Ultra-violet
Visible light
X-rays
(4)
(b)
Microwaves are another type of electromagnetic radiation.
Calculate the frequency of microwaves of wavelength 3 cm.
(The velocity of electromagnetic waves is 3 × 108 m/s.)
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(Total 8 marks)
Q3.
After a person is injured a doctor will sometimes ask for a photograph to be taken of the
patient’s bone structure, e.g. in the case of a suspected broken arm.
(i)
Which type of electromagnetic radiation would be used to take the photograph?
.....................................................................................................................................
(1)
(ii)
Describe the properties of this radiation which enable it to be used to photograph bone
structure.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 3 marks)
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Q4.
The diagram shows a small part of the electromagnetic spectrum divided into seven
sections.
The different properties of the waves in each section make them useful in different ways.
The waves in which section, A, B, C, D, E, F or G, are:
(a)
used to send a signal to a satellite in space
.........................................
(1)
(b)
used to communicate with a submarine under the water
.........................................
(1)
(c)
used by a radio station to broadcast programmes around the world
.........................................
(1)
(d)
the waves with the shortest wavelength?
.........................................
(1)
(Total 4 marks)
Q5.
(a) Scientific research carried out in 13 countries has tried to find out if there are any
links between using a mobile phone and developing different types of cancer.
About 13 000 people, half with cancer and half in good health, were interviewed about
their mobile phone use.
(i)
Suggest why people in good health were interviewed.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(1)
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(ii)
Interviewing 13 000 people gave the researchers a large sample size.
Give one advantage, in any research project, of having a large sample size rather
than a small sample size.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(1)
(b)
The following information was included in a newspaper article about the research project.
•
It may be difficult to prove there is a link simply by asking people how much
they use a mobile phone. People’s memories are not always accurate.
•
Scientists in Israel found that people who use a mobile phone a lot are 50%
more likely to develop a cancer on the salivary gland just in front of the ears.
•
The cost of the research, £20 million, has been partly paid for by mobile
phone companies.
•
No children were included in the research.
(i)
Draw a ring around the correct answer to complete the following sentence.
environmental
Using children in scientific research raises
ethical
issues.
social
(1)
(ii)
Suggest two reasons why some people are concerned that the research was partly
paid for by mobile phone companies.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
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(iii)
In Germany, mobile phones that emit very low levels of radiation are marked with a special symbol.
Explain why low emission mobile phones should be marked in this way.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(Total 7 marks)
Q6.
The table shows the electromagnetic spectrum.
Three types of wave have been missed out.
(i)
Use words from the box to complete the table.
infra red rays
radio waves
X-rays
(2)
(ii)
Which one of the following gives a use of gamma rays?
Put a tick ( ) in the box next to your choice.
to communicate with satellites
to see objects
to kill cancer cells
(1)
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(iii)
Complete the following sentence by drawing a ring around the correct word in the
box.
energy
All electromagnetic waves move gases
from one place to another.
particles
(1)
(Total 4 marks)
Q7.
(a) An endoscope is an instrument used by doctors for looking inside patients. A bundle
of thin optical fibres pass light into the patient’s body, a second bundle of fibres carry reflected
light back to the doctor.
(i)
Complete the diagram below to show how an optical fibre is able to pass light into a
patient’s body.
(2)
(ii)
Give one advantage of using lots of thin fibres to make the bundles, rather than a
few thick fibres.
............................................................................................................................
............................................................................................................................
(1)
(iii)
Give one further example of the practical use of an optical fibre.
............................................................................................................................
............................................................................................................................
(1)
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(b)
The diagram shows a wave travelling through a stretched spring.
In what way is this wave the same as a sound wave?
.....................................................................................................................................
(1)
(c)
Sound waves travel faster in liquids than in gases. Why?
.....................................................................................................................................
.....................................................................................................................................
(1)
(d)
A bat uses ultrasound to find its way around. Explain how.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 8 marks)
Q8.
The picture shows a horse being prepared for an X-ray.
The person who will take the X-ray and the person holding the horse are wearing special
aprons. These aprons have a lead lining.
Explain why the lead lining is important.
To gain full marks in this question you should write your ideas in good English.
Put them into a sensible order and use the correct scientific words.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
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(Total 3 marks)
Q9.
Both X-ray machines and CT scanners are used to produce images of the body.
(a)
The diagram shows an X-ray photograph of a broken leg.
Before switching on the X-ray machine, the radiographer goes behind a screen.
Explain why the radiographer does this.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(b)
The following is an extract from a newspaper article.
X-rays cause 700 new cancers each year in the U.K.
Each year there are about 125 000 new cancer cases in the UK, of
which, about 700 may be due to the use of X-rays to diagnose
illness.
The article was reporting on a scientific research project first published in a medical
journal.
What evidence would the scientists have collected to come to the conclusion that X-rays
can cause cancer?
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
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........................................................................................................................
(2)
(c)
Explain the advantage of a CT scan compared to an X-ray.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)
(Total 7 marks)
Q10.
(a)
Microwaves are one type of electromagnetic wave.
(i)
Which type of electromagnetic wave has a lower frequency than microwaves?
...........................................................................................................................
(1)
(ii)
What do all types of electromagnetic wave transfer from one place to another?
...........................................................................................................................
(1)
(b)
The picture shows a tennis coach using a speed gun to measure how fast the player
serves the ball.
(i)
The microwaves transmitted by the speed gun have a frequency of 24 000 000 000
Hz and travel through the air at 300 000 000 m/s.
Use the equation in the box to calculate the wavelength of the microwaves emitted
from the speed gun.
wave speed = frequency × wavelength
Show clearly how you work out your answer.
...........................................................................................................................
26
...........................................................................................................................
(ii)
Wavelength = .............................. m (2)
Some of the microwaves transmitted by the speed gun are absorbed by the ball.
What effect will the absorbed microwaves have on the ball?
...........................................................................................................................
...........................................................................................................................
(1)
(iii)
Some of the microwaves transmitted by the speed gun are reflected from the
moving ball back towards the speed gun.
Describe how the wavelength and frequency of the microwaves change as they are
reflected from the moving ball.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 7 marks)
(a)
The wavelengths of four different types of electromagnetic wave, including visible light
waves, are given in the table.
Type of wave
Wavelength
Visible light
0.0005 mm
A
1.1 km
B
100 mm
C
0.18 mm
Which of the waves, A, B or C, is an infra red wave?
....................................
(1)
(b)
A TV station broadcasts at 500 000 kHz. The waves travel through the air at
300 000 000 m/s.
Use the equation in the box to calculate the wavelength of the waves broadcast by this
station.
wave speed = frequency × wavelength
Show clearly how you work out your answer.
.....................................................................................................................................
27
.....................................................................................................................................
(c)
Wavelength = .............................. m(2)
What happens when a metal aerial absorbs radio waves?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(d)
Stars emit all types of electromagnetic waves. Telescopes that monitor X-rays are
mounted on satellites in space.
Why would an X-ray telescope based on Earth not be able to detect X-rays emitted from
distant stars?
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 6 marks)
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Mark scheme
M1.
(a)
gamma rays above x-rays
M3.
for 1
mark
(i)
X-rays or gamma rays
for 1 mark
1
(b)
-1
upper radio wave boundary correct (10 m) (±
1mm)
(ii)
for 1
mark
(c)
passes through flesh;
stopped by bone/absorbed
for 1 mark
each
2
visible radiation/light
[3]
• within the middle third of a wavelength
band
M5.
(a)
(i)
• in the correct wavelength range (10-6 –
10-7m)
to compare mobile phone usage between
the two groups
1
(ii)
enough data to indicate relationships
or
reduce effect of anomalous data
1
each
for 1
mark
(d)
ultraviolet between *visible radiation and X-rays
(b)
(i)
ethical
1
for 1
mark
(ii)
(e)
microwaves above *radio waves and below
*infra red
(*not necessarily immediately)
negative effects on health may not get
published
for 1
mark
(f)
research may be biased (in favour of
companies)
1
accept
negative
effects on
health
may be
played
down
between 108Hz + 107Hz and nearer to 108Hz
than to 107Hz
gains 1
mark
[7]
1
M2.
(a)
radio – 1500
ultra violet 3 × 10–8
visible – 5 × 10–7
X-rays – 1 × 10–11
(iii)
4
(b)
it allows people to easily identify lower
risk phones
1
and this allows people to make a more informed choice
1 × 1010Hz 1010HzOK
accept and this allows a comparison to be
made
for 4
marks
1
[7]
else 1 × 10
10
M6 (i)
X-rays
infra red (rays)
radio (waves)
for 3
marks
all three in correct order
else 3 × 108/0.03
allow 1
mark for 1
correct
for 2
marks
2
8
else v = frequency × wavelength or 3 × 10 =
0.03f
any answer with unit Hz scores 1, 2 or 3
(ii)
to kill cancer cells
1
for 1
mark
(iii)
energy
1
4
[8]
[4]
29
M7.
(a)
reflections)
total internal reflection shown (2 – 8
(i)
M8.
1
1
angles look correct (by eye) (2 – 5
reflections)
1
(ii)
X-rays do not go through lead
accept lead protects them from the X-rays
accept not exposed to X-rays
1
can be bent more (without loss of light)
accept easier to get into patient or more
flexible
accept more detailed or better image
accept if some fibres broke system would
not fail
do not accept to pass more light - neutral
lead stops / reduces risk of X-rays harming / damaging /
killing (persons) cells
accept X-rays (may) cause cancer
accept organs for cell
do not accept references to electric shock
do not accept stops bones of people showing
on X-ray
answers involving the horse wearing an apron
are incorrect
1
(iii)
Quality of written communication
award for a sensible sequence of two points
any one of the following:
do not accept any further endoscopy uses
references to gamma rays are incorrect
1[3]
(telephone) communications (carry (laser) light) for surgery
or operations
torches
guides in cars
table lamps or ornamental lights
M9.
do not accept telephone wires
accept cause cancer
(a)
1
carry TV signals
carry computer data or information
cable TV or cable telephone
any stray X-rays are absorbed by screen
1
do not accept TV or telephone or
computers without qualification
which reduces the radiation dose to the
radiographer
1
do not accept bomb disposal unless
qualified
accept to stimulate children with learning
difficulties
(b)
(b)
X-rays are ionising
or
X-rays kill / damage cells
medical records / X-ray records
1
(both) longitudinal
accept both have compressions or
rarefactions
accept both have high or low pressure
regions
accept both transfer energy
do not accept 'need a medium'
of people with cancer
1
(c)
a CT scan gives a 3D image
1
1
(c)
therefore the image can be observed from different directions
1
liquids have a greater density
[7]
or
M10.
(a)
(i)
radio(waves)
molecular spacing in gases is greater
1
(ii)
1
energy
correct answer only
(d)
1
(bat) transmits or emits ultrasound or pulses or
signals or sound or waves
(b)
allow one mark if response is in terms of
distance and time
(i)
0.0125 (m)
allow 1 mark for correct transformation and
substitution
1
2
picks up reflected ultrasound or signals or
waves or sound or echo
(ii)
allow 1 mark for echo location
1
[8]
make it hot(ter)
do not accept cook it
accept (air) particles inside ball will move faster
accept water in the ball gets hotter
1
(iii)
wavelength decreases
ignore
reference
to speed
1
frequency increases
1
[7]
30
M11.
(a)
C or 0.18 mm
1
(b)
0.6 m
allow 1 mark for correct transformation and
substitution
allow 1 mark for changing frequency to Hz
answer 600 gains 1 mark
2
(c)
creates an alternating current
accept ‘ac’ for alternating current
accept alternating voltage
1
with the same frequency as the radio wave
accept signal for radio wave
or it gets hotter
1
(d)
X-rays cannot penetrate the atmosphere
accept atmosphere stops X-rays
do not accept atmosphere in the way
or X-rays are absorbed (by the atmosphere)
before reaching Earth
ignore explanations
1
[6]
Communicate - stay in touch Answers
1a)
Short
wavelength
Long
wavelength
gamma rays
X-rays
ultraviolet
visible
infra-red
microwaves
radio waves
10-14 m
10-10 m
10-8 m
10-6 m
10-5 m
10-2 m
103 m
b
i Transverse, carry energy, diffract, reflect and refract.
ii Gamma rays.
iii frequency = wave speed / wavelength
frequency of radio waves =
v
= 3  105 Hz

frequency of microwaves = 3 x 1010 Hz
students may use ratios to show this.

31
2a
e.g.
b
Above 300 MHz.
c Radio waves reflect from the ionosphere then reflect off the Earth and may take several ‘hops’
(reflections) to travel to the other side of the Earth.
d The radio wave is reflected by the ionosphere. The ionosphere changes its ability to reflect. It may
move up or down or disappear for a time.
e In absorption, the energy of the wave is transferred to an object – usually causing the object to heat
up. Reflection is the bouncing back of the wave.
f
Mobile phones, Bluetooth, communicating with computers etc.
Discussion
Possible answers include:
Skin cancer, death of some species of animals caused by more ultraviolet radiation reaching the Earth’s
surface.
Greenhouse warming is caused by gases such as carbon dioxide which ‘trap heat’, i.e. do not allow infrared radiation to escape from the Earth. Loss of the ozone layer allows more ultraviolet radiation to reach the
Earth because it is, at present, absorbed by the ozone layer.
32