Electromagnetic Waves
Name____________________
Q1.
The electromagnetic spectrum is made up of waves with different wavelengths and
frequencies.
(a)
Draw one line from each type of electromagnetic wave to a use of that type of wave.
Electromagnetic
wave
Use
Cooking food
Radio waves
Detecting broken bones
Visible light
Fibre optic communications
X-rays
Transmitting TV programmes
(3)
A student investigated how the type of surface affects the amount of infrared the surface
radiates.
The student used a hollow metal cube.
Four of the surfaces of the cube were different.
This is the method used.
1.
Fill the cube with hot water and seal it with a lid.
2.
Measure the infrared radiation emitted from each surface using an infrared detector.
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The diagram below shows the equipment used.
(b)
Table 1 shows some of the variables in this investigation.
Table 1
Variable
Independent
Distance between
infrared detector and
surface of cube
Dependent
Control
✓
Starting temperature of
water inside cube
Temperature measured
by infrared detector
Type of surface
Identify each variable as an independent, dependent or control variable.
Tick (✓) one box in each row on Table 1.
One row has been completed for you.
(3)
Table 2 shows the results.
Table 2
Type of surface
Temperature in °C
Shiny black
66.5
Matt white
61.0
Matt black
69.0
Shiny silver
26.0
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(c)
What was the resolution of the infrared detector?
Tick (✓) one box.
0.5 °C
1.0 °C
26.0 °C
66.5 °C
(1)
(d)
What was the range of temperatures recorded?
Range = _______________ °C to _______________ °C
(1)
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(e)
Complete the chart below.
You should:
•
plot the data from Table 2 as a bar chart
•
label each bar.
(3)
(f)
Give one conclusion that can be made from the results in Table 2.
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(1)
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(g)
Which equation links frequency (f), wavelength (λ) and wave speed (v)?
Tick (✓) one box.
f=v×λ
v=f×λ
(1)
(h)
A radio wave has:
•
a speed of 300 000 000 m/s
•
a wavelength of 500 m
Calculate the frequency of the radio wave.
Give the unit.
Choose the unit from the box.
hertz
kilograms
metres
seconds
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Frequency = _______________ Unit _______________
(4)
(Total 17 marks)
Q2.
X-rays and gamma rays are types of electromagnetic waves.
X-rays are used for medical imaging.
(a)
Which substance will not absorb X-rays?
Tick (✓) one box.
Bone
Metal
Skin
(1)
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The table below shows the effect of exposure to different doses of radiation.
Dose in mSv
Effect on the human body
100
slightly increased risk of
cancer
1000
5% increased risk of cancer
5000
high risk of death
(b)
During one X-ray a person receives a dose of 0.100 mSv
Why is this dose unlikely to harm the person?
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(1)
(c)
A doctor takes an X-ray photograph of a person.
When taking the X-ray photograph, the doctor stands behind a screen.
Suggest why.
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(1)
(d)
Which of the following are gamma rays used for?
Tick (✓) one box.
Cooking food
Energy-efficient lamps
Sterilising medical equipment
(1)
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(e)
Why are gamma rays and X-rays harmful to humans?
Tick (✓) one box.
They are ionising
They are radioactive
They travel at the speed of light
(1)
(f)
Electromagnetic waves are also used in communications.
Describe how microwaves and visible light are used in communications.
Microwaves ________________________________________________________
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Visible light _________________________________________________________
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(4)
(Total 9 marks)
Q3.
Infrared and microwaves are two types of electromagnetic radiation.
(a)
State one example of the use of each type of radiation for communication.
Infrared: ______________________
Microwaves: ___________________
(2)
(b)
Some of the properties of infrared and microwaves are the same.
State two of these properties.
1. _________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
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(2)
(Total 4 marks)
Q4.
A solar water bag can be used to heat water for an outdoor swimming pool.
A student wanted to find out if the colour of the solar water bag affects the temperature
increase of the water inside the bag.
The diagram below shows some of the equipment used.
This is the method used.
1.
2.
3.
4.
Fill each bag with water.
Place the four bags on the ground outside.
After three hours, measure the temperature of the water inside each bag.
Repeat steps 1−3 on the next two days.
(a)
Suggest three changes the student should make to this method to get valid results.
1. _________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
___________________________________________________________________
3. _________________________________________________________________
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(3)
The student repeated the investigation using an improved method.
The results obtained were valid.
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The table below shows the results.
Colour of
bag
(b)
Temperature increase in °C
Day 1
Day 2
Day 3
Mean
Black
44.0
31.4
43.4
39.6
Pale blue
38.5
23.6
38.1
33.4
Pale green
37.9
23.7
37.7
33.1
White
25.3
23.4
24.2
X
The student used a thermometer to measure the temperature of the water inside
each bag.
What was the resolution of the thermometer?
Resolution = _____________ °C
(1)
(c)
Suggest one reason why the temperatures increased less on Day 2 than on Day 1
and Day 3.
___________________________________________________________________
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(1)
(d)
Calculate the mean temperature increase for the white bag.
___________________________________________________________________
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Mean temperature increase = _____________ °C
(1)
(e)
Which colour of bag would be best to use to heat water?
Give a reason for your answer.
Colour ____________________________________________________________
Reason ____________________________________________________________
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(2)
(Total 8 marks)
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Q5.
A baby monitor has a sensor unit that transmits an image of the baby and the noises the
baby makes to a monitor unit.
The monitor unit then displays an image of the baby and emits the noises the baby
makes.
(a)
Compare the properties of the waves that transmit images and noises from the
monitor unit.
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(4)
(b)
The sensor unit can detect infrared and visible light.
Suggest one advantage of being able to detect infrared.
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(1)
(c)
Write down the equation that links frequency, wave speed and wavelength.
Equation ___________________________________________________________
(1)
(d)
The signals for the monitor unit are transmitted as electromagnetic waves with a
wavelength of 0.125 m.
Wave speed of electromagnetic waves = 3 × 108 m / s
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Calculate the frequency of the signal.
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Frequency = __________________ Hz
(3)
(Total 9 marks)
Q6.
There are different types of electromagnetic wave
(a)
Which type of electromagnetic wave has the shortest wavelength?
___________________________________________________________________
(1)
(b)
A new technology has been developed to charge small electrical devices from the
radio waves in the air around us.
Explain how radio waves could charge a small electrical device.
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(2)
The figure below shows the wavefronts of a light wave passing through air into a glass
block.
(c)
Complete the figure to show the wavefronts as they pass out into the air.
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(2)
(d)
Explain why there is refraction at the boundary between air and glass.
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(3)
(e)
The period of a wave in a ripple tank was measured.
The period of the wave was 420 ms
The speed of the wave was 0.60 m/s
Calculate the wavelength of the wave.
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___________________________________________________________________
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Wavelength = ____________________ m
(5)
(Total 13 marks)
Q7.
The electromagnetic spectrum is made up of waves with different wavelengths and
frequencies.
(a)
Give the type of electromagnetic wave with the lowest frequency.
___________________________________________________________________
(1)
(b)
A wave has a wavelength of 2.5 km and a velocity of 300 000 000 m/s
Calculate the frequency of the wave.
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Frequency = _______________ Hz
(4)
(c)
The diagram below shows equipment that is used to investigate the emission of
infrared radiation from different colours of surface.
The four hollow metal cubes are each painted a different colour.
The cubes can be filled with hot water before the lid is put on.
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Describe a method to investigate which colour of surface emits infrared radiation at
the greatest rate.
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(4)
(d)
Which colour of surface will emit infrared radiation at the greatest rate?
Tick (✓) one box.
Black
Blue
Orange
White
(1)
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(e)
It is important to identify people at airports who may have infectious diseases, such
as measles.
Explain how cameras that detect the rate of infrared emission can identify people
with infectious diseases such as measles.
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(2)
(Total 12 marks)
Q8.
X-rays form part of the electromagnetic spectrum.
Radiographers use X-rays to produce images of bones inside the body.
(a)
Explain why X-rays can be used to produce images of the bones inside the body.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(b)
The table below shows the effect of exposure to different doses of radiation.
Dose in mSv
Effect on the human body
100
slightly increased risk of
cancer
1000
5% increased risk of cancer
5000
high risk of death
During an X-ray a person receives a dose of 0.5 mSv
The radiographer takes many X-ray images each day.
Explain why the radiographer stands behind a protective screen when taking an Xray image.
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Page 15 of 24
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(3)
(c)
Radio waves form part of the electromagnetic spectrum.
The diagram below shows one use of radio waves.
Explain how electrical signals in the transmitter produce a signal in the receiver.
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(3)
(Total 8 marks)
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Mark schemes
Q1.
(a)
additional line from a box on the left negates the mark for that box
3
(b)
Variable
Independent
Dependent
Control
Distance between
infrared detector and
surface of cube
Starting temperature of
water inside cube
✓
Temperature measured
by infrared detector
✓
✓
Type of surface
1
1
1
do not accept more than one tick per row
(c)
0.5 °C
1
(d)
any one from:
•
26(.0 °C to) 69(.0 °C)
•
69(.0 °C to) 26(.0 °C)
ignore 43(.0 °C)
1
(e)
3 bars correctly plotted
allow a tolerance of +/- ½ of a small square
allow any width, bars touching or not
allow 1 mark for 2 bars correctly plotted
2
3 bars correctly labelled
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1
(f)
any one from:
•
matt black is the best emitter / radiator
allow silver is a poor emitter / radiator
•
shiny silver is the worst emitter / radiator allow black is a good emitter /
radiator
allow an answer in terms of highest / lowest
temperature
allow matt white and shiny black are (almost) the
same at emitting / radiating
ignore any reference to absorption / reflection
1
(g)
v=f×λ
1
(h)
300 000 000 = f × 500
1
f=
1
f = 600 000
1
hertz / Hz
1
[17]
Q2.
(a)
skin
1
(b)
dose is much lower than even slight increased risk of cancer dose
allow much less than 100 mSv
1
(c)
to reduce the dose of radiation (they are exposed to)
allow reduce the risk
1
(d)
sterilising medical equipment
1
(e)
they are ionising
1
(f)
microwaves
data is transmitted / detected
allow signal / information for data
1
by (mobile) phone / WiFi / satellite
allow bluetooth
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1
visible light
example of device / system
1
description of how light is used
e.g. the internet transfers information via visible
light in fibre optics
e.g. image produced / seen on a TV / mobile
phone
allow any sensible suggestion for visible light, but
the two marks must be linked
1
[9]
Q3.
(a)
use of infrared:
remote controls
fibre optic (communications)
1
use of microwaves:
mobile/cell phones
accept mobiles
accept phone signals
satellite (communications/TV)
wi-fi
Bluetooth
1
(b)
any two from
•
same speed
or
travel at the speed of light (in a vacuum)
•
transverse
accept a full description of a transverse wave
•
transfer energy (from one place to another)
•
can be reflected
•
can be refracted
•
can be diffracted
•
can be absorbed / transmitted
•
can travel through a vacuum/space
•
can be polarised
travels in straight lines is insufficient
2
[4]
Q4.
(a)
any three from:
•
same surface area of bag (exposed to sun)
allow same sized bag
Page 19 of 24
•
same volume / mass of water
allow same amount of water
•
use same starting temperature of water
allow measure temperature at the start
•
•
•
•
•
place all bags out at the same time
place all bags out in same area / conditions
same thickness of material / bag
same type of material (for each bag)
use IR lamp in a lab
3
(b)
0.1 (°C)
1
(c)
any one from:
•
more cloudy
•
less sunny
ignore less Sun
•
•
less sunlight
cooler day
1
(d)
24.3 (°C)
1
(e)
black
1
(it has the) greatest (temperature) rise
allow it is the best absorber of IR (radiation)
ignore best emitter of IR (radiation)
1
reason only scores if black is given
[8]
Q5.
(a)
any four from:
•
•
•
•
•
light waves are transverse whereas sound waves are longitudinal
light waves travel faster than sound waves
light waves have a higher frequency than sound waves
light waves have a shorter wavelength than sound waves
light waves have oscillations perpendicular (to the direction of energy transfer)
whereas sound waves are parallel (to the direction of energy transfer)
4
(b)
the baby can be seen in the dark
1
(c)
wave speed = frequency × wavelength
accept v = f λ
1
(d)
3 × 108 = f × 0.125
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1
f = 3 × 108 / 0.125
1
f = 2.4 × 109 (Hz)
allow 2.4 × 109 with no working for 3 marks
1
[9]
Q6.
(a)
gamma (waves / rays)
allow correct symbol
1
(b)
small device absorbs / receives the radio waves
allow aerial absorbs / receives radio waves
1
which creates an alternating current of the same frequency (as the radio
waves)
1
(c)
direction of wave is parallel to the wave entering the block and forms a
continuous line
1
wavefronts leaving glass block shown same distance apart as when entering
the block
1
(d)
wave(front) slows down in glass
allow solid for glass
allow more dense material
1
one edge of the wavefront enters the glass before the other
1
(therefore) one edge of the wave(front) slows down before the other, so the
wave changes direction
allow bends for changes direction
1
if no other mark awarded allow 1 mark for
wave(front) changes speed and changes
direction when it crosses a boundary
(e)
an answer of 0.25 (m) scores 5 marks
T = 0.42 s
1
f = 2.38
allow a correctly calculated value using an
incorrectly / not converted value of T
1
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0.60 = 2.38 × λ
allow use of their value of f calculated using
for this and subsequent steps
1
1
λ = 0.25 (m)
allow an answer that rounds to 0.25 (m)
consistent with their calculated value of f using
1
alternative method
T = 0.42 s (1)
distance = speed × time (1)
allow s = v × t
distance is wavelength and time is period of the
wave (1)
λ = 0.60 × 0.42 (1)
λ = 0.25 (m) (1)
[13]
Q7.
(a)
radio (waves)
1
(b)
2.5 km = 2500 m
1
300 000 000 = f × 2500
this mark may score if λ is not/incorrectly
converted
1
f=
this mark may score if λ is not/incorrectly
converted
1
f = 120 000 (Hz)
or
f = 1.2 × 105 (Hz)
allow an answer consistent with their value of λ
1
(c)
Level 2: The method would lead to the production of a valid outcome. The key
steps are identified and logically sequenced.
3−4
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Level 1: The method would not necessarily lead to a valid outcome. Most steps are
identified, but the plan is not fully logically sequenced.
1−2
No relevant content.
0
Indicative content
Measurements
•
take reading of temperature using infrared detector (and record)
•
repeat with each cube
Control variables
•
cubes same volume
•
cubes made of same metal
•
add same volume of (hot) water
•
add water at same temperature
•
distance of detector from surface
•
air temperature
•
thickness / type of paint
•
leave for same amount of time or record every minute
Methods with only measurements or only control variables are limited to Level 1
(d)
black
1
(e)
(people with measles / infections) have raised temperature
allow people with measles / infections have fever
1
(so) emit infrared (radiation) at a greater rate
ignore emit more infrared (radiation) unqualified
1
[12]
Q8.
(a)
X-rays are absorbed by bone
1
but can pass through flesh
ignore skin
1
(b)
taking lots of X-rays would give a large dose
1
which would increase the radiographer’s risk
1
the screen absorbs some of the X-rays
allow screen reduces the risk/dose received by
the radiographer
1
(c)
electrical current / oscillations in the transmitter producing radio waves
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1
radio waves are absorbed by the receiver inducing electrical current / oscillations in
the receiver
1
at the same frequency
if no other mark is awarded, allow 1 mark for
radio waves transfer information/energy through
the air
1
[8]
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