Required
10
Background Knowledge
Practical 10: Radiation and Absorption
2
Visible light
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ee
KADER
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heat-proof
aiiat
© CGP — not to be photocopied
/
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Infrared radiation
A type of electromagnetic wave.
It transfers energy between the
thermal energy stores of objects.
Key Definition
Temperature will decrease, as there is less radiation from the sun, due to that side of the earth
facing away from the sun and not in its direction.
Explain how the temperature of this part of the Earth’s surface
changes at night time. You could include a diagram in your answer.
J
Radiation emitted from the sun increases during the day, as that
side of the earth is facing in the direction of the sun, which is
an extremely hot object.
Explain why the temperature of this part of the Earth’s surface
increases during the day.
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_
experiment repeatable and reproducible.
Discuss
Practical 10: Radiation and Absorption
How do you think this works?
under the Leslie cube also helps make
As well as protecting the work surface, placing a heat-proof mat
with your partner.
Hint: the kettle isn’t for making cups of tea...
© CGP — not to be photocopied
<a
E>
L
Control variable
A variable that you
keep the same.
Key Definition
Fill a leslie cube up with hot water, do not touch to avoid burns, measure the radiation of each
surface from all sides, using an infrared detector ensure the infrared detector is at a perpendicular
angle to the leslie cube surface and of equal distance all the way round to keep things fair.
Record in a table and plot a bar chart.
how surface properties affect the infrared radiation emitted from that surface.
Control variables
with each face
water in contact
Temperature of the
Add more control variables of the experiment to the mind map below.
Task 6 Write a practical method using the set-up in the diagram above to investigate
5
Electromagnetic waves can transfer energy through a vacuum.
Task
te
kettle
[_]
To ensure equal distance all the way round between the infrared detector and the leslie
Leslie cube. The Leslie cube is centred in the square. Explain the purpose of the square.
<—
than it should.
Practical 10: Radiation and Absorption
Sia
XX
(-
.
Electromagnetic waves transfer energy and matter.
from the Sun, and emitting infrared radiation into the atmosphere.
(—
<p
In the diagram above, there’s a dotted square that has been drawn on the paper around the
paper
——S >
T0100)
different surface properties,
PU
L]
frequency
Gamma
infrared detector
e shiny black
cube, this is to avoid the infrared detector being too far or too close, detecting less or more
X-rays
Leslie cube
e shiny silver
Electromagnetic waves transfer energy but not matter.
ultraviolet
wavelength
e matt white
[_]
Tick the box next to each true statement below.
infared
Task 3 The hotter an object, the more infrared radiation it emits
in a given time. The diagram on the right shows a part of the Earth’s
surface where it is day time, absorbing infrared radiation emitted
Task
frequency
microwaves
;
e matt black
Required
19
Practical 10
EEO
Peay dui
A Leslie cube isahollow
~
metal box that can be fille
d
with hot water. Each of
the four vertical faces have
The diagram below shows an experimental set-up that can be used to measure the
The properties of the four vertical surfaces are:
4
infrared radiation emitted from the four different vertical surfaces of a Leslie cube.
Task
7| Heetatitanas
wavelength
Long
Task 1 Complete the electromagnetic (EM) spectrum below.
Infrared radiation is a type of electromagnetic (EM) wave that all objects emit and absorb. In this practical,
you'll investigate how the properties of a surface affect the amount of infrared radiation it emits or absorbs.
Practical
78
VELL
P ttt,
Required
10
Results and Analysis
9.5
42
18.0
Matt white
Shiny silver
Shiny black
14.4
39
a4
18.5
Repeat 2
14.3
4.0
54
18.7
Repeat 3
139
43
39
18.9
Repeat 4
Mean
Key Definition
Anomalous result
A result that doesn’t
seem to fit with the
rest of the data.
AMITITLELI LITLE Ty
I
When choosing a araph, 4
think about the type of
data you have and how you
can use the graph to draw
conclusions from your results,
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Practical 10: Radiation and Absorption
a numerical value that can be ordered, so no line graph possible.
© CGP — not to be photocopied
Explain why the type of graph you've chosen is suitable for these results.
Bar chart as it clearly shows the difference in intensity between the surfaces. The surfaces aren't
Task 8 Plot a suitable graph of Sarah’s results on the graph paper below.
18.8
Matt black
Repeat 1
Infrared intensity (W/m?)
Circle any anomalous results and calculate the mean infrared intensities emitted for each surface.
Surface type
table below.
Task 7 Sarah used the set-up on the previous page to measure the infrared radiation emitted from each
vertical surface of the Leslie cube. She repeated the experiment three more times and recorded her results in the
Practical
80
I
MITT,
black surface.
Radiators are more efficient when they are painted black / white, because they will emit
less / more radiation, warming the room more efficiently.
2)
© CGP — not to be photocopied
.
Practical 10: Radiation and Absorption
over time.
therefore will emit less infrared radiation
As temperature lowers, the can gets cooler,
Sketch a graph of the results you’d expect from Cory’s experiment and explain them.
Va
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Each can should be filled with the same amount of water
All starting temperatures should be the same
Explain two things Cory must do to make sure his experiment is a fair test of emission.
Task 11 Cory is investigating the emission of radiation from different surfaces. Instead of the intensity
of radiation, he plans to measure the change in temperature over time. He uses four cans made from the
same material. Each can is covered with one of the four different surfaces. He fills each can with boiling
water and records the temperature of the water every 30 seconds for 10 minutes.
XN
10
Circle the correct words to suggest and explain the most suitable material properties for each use
shiny
Required
Practical
Thermal blankets should be matt black / shiny silver. They need to minimise the energy radiated
from a person, so should be made of a material that is a good / poor emitter and absorber.
10
matt
more
The black surfaces emit ..........c00060000.
radiation than the other coloured surfaces.
Fill in the gaps to complete the two conclusions you can draw from Sarah’s results.
and Evaluation
1)
Task
Task 9
Conclusions
81
Required
Exam-Style Questions
elle ow om ww set wp tos uo tet vce ¢ soir a :
heat
proat wnat
infrared detector
——<—
—-—
i
kettle
influence the amount of infrared radiation it will emitt.
To ensure each surface receives the same amount of thermal energy, as it will
Explain why the student should make sure the four vertical faces of the Leslie cube are at the
same temperature before taking any measurements.
Less radiation will be detected
Predict what would happen if the student moved the infrared detector further away from the
Leslie cube.
energy is maintained.
The lid will ensure the water does not cool down too quickly, the lid makes sure thermal
A Leslie cube has a lid with a small hole in it for filling the cube. Explain why having a lid on
the Leslie cube gives more accurate results than an open cube.
paper
Leslie cube
A student was investigating the effect of the type of surface on its interaction with
infrared radiation, using the set-up below. The infrared detector can measure the
intensity of infrared radiation.
Practical 10: Radiation and Absorption
[Total 7 marks]
© CGP — not to be photocopied
absorb the most light and the most energy. Increasing its emitting of radiation.
Is the student's conclusion valid? Explain your answer.
Yes, matt black surfaces are the best absorbers and emitters of radiation as black surfaces will
absorber of radiation.
1.4 The student gets the highest reading from the detector from the matt black side,
and concludes that the matt black surface must be the best emitter and best
1.3.
1.2
1.1
1
Task 12 Try these exam-style questions.
Practical 10
82
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