National 4-5
Homework
Homework 1
1.
2.
3.
Unit 2b – Nuclear Radiation
Homework 2
There are three main types of ionizing radiation.
a) Name the three types.
b) Which type causes most ionization?
c) Describe an experiment which distinguishes between the
three types.
The following counts per minute were measured in a room
when no source was present:
18, 21, 17, 18, 19, 23, 18, 21, 15, 20
a) Calculate the average count rate.
b) Explain why there is a background count rate.
c) Why is it not constant?
1.
Name the three types of radiation and explain which of the
three types of radiation causes the most ionization.
1.
What effects can nuclear radiation have on living cells? Give
two medical uses of nuclear radiation based on this effect.
2.
Describe one medical application of nuclear radiation based on
the fact that it is easy to detect. How could this same
application be used in the airline industry?
3.
Explain what is meant by a tracer and describe how tracers
can be used in medicine.
4.
Draw a chart to illustrate the different sources of
background radiation, showing how each source contributes to
the total background radiation. Explain how the level of
background radiation can change with: geography, weather,
man-made events etc.
5.
Describe an experimental method for measuring background
radiation.
A student obtained the following results when he placed
different absorbers between radioactive sources and a
Geiger-Muller detector.
Absorbing
Material
Air only
Air only
Paper
Aluminium
Lead
a)
b)
c)
Count Rate in c.p.m.
no source present – 20
Source A
Source B
Source C
678
445
1890
690
19
1345
682
21
28
122
18
19
Which source emits only alpha radiation?
What type of radiation is emitted by source C?
Why does the count rate with source A present not
come down to the background rate, even when a lead
absorber is used?
National 4-5
Homework
Homework 3
1. Absorbed dose is measured in units called grays, Gy.
a) Write an equation for absorbed dose and explain what
the different terms in the equation mean..
b) Explain what is meant by the term “absorbed dose”.
c) A patient undergoing radio-therapy receives a dose of
1 Gy. What dose this mean?
d) Apart from absorbed dose, what other factors effect
the risk of biological harm from exposure to radiation?
2.
Dose equivalent is measured in units called sieverts, Sv.
a) Write an equation for dose equivalent and explain what
the different terms in the equation mean.
b) Explain what is meant by the term “dose equivalent”.
3.
A nuclear power station worker, whose mass is 75 kg, is
exposed to 450 mJ of radiation. What is his absorbed dose?
4.
A patient is receiving radio therapy for a brain tumour. A
beam of gamma ray radiation is directed at the tumour. If
the mass of the tumour is 200 g and he needs to receive a
does of 40 mGy, how much energy should the beam of
radiation be given?
5.
6.
Over the course of a month a technician in a hospital
radiography department is exposed to 126 μGy of β radiation.
Work out the dose equivalent of this.
A patient is exposed to 70 μGy of radiation which gives a
dose equivalent of 1.4 mSv. What type of radiation was she
exposed to? (hint: work out the weighting ratio)
Unit 2b – Nuclear Radiation
Homework 4
1.
The activity of a source is measured in Becquerels. Explain
what is meant by the “activity of a source” and explain what
an activity of 1 Bq means.
2.
What is the activity of a source if 45 000 atoms decay in
1 minute?
3.
What is the activity of a source if there are 17 million atoms
decaying in 5 minutes?
4.
If the activity of a source is 25 kBq, how many atoms decay in
30 s?
5.
The activity of a source is 30 MBq. How many atoms decay in
5 minutes?
6.
Explain why the activity of a source falls over time and what
is meant by the half-life of a source.
7.
A radioactive source has a half-life of 12 hours. If the
source has an initial activity of 8000 Bg, find the activity
after 2 days.
8.
The activity of a radioactive sample decreases from 2000 Bq
to 125 Bq over a period of 40 minutes. What is the half-life
of the sample?
9.
The half-life of a carbon14 sample is 5700 years. If a sample
of bone has been analysed and the % of carbon 14 in it is
found to be 1/8th of that in the atmosphere, approximately
how old is the bone?
National 4-5
Homework
Homework 5
1.
Unit 2b – Nuclear Radiation
3.
A radioactive source is used for medical treatment.
The graph shows the activity of this source over a
period of time.
An experiment is carried out to measure the half-life of a
source in an area with high background radiation. The
following results were obtained – the count rate has NOT
been corrected for background radiation.
Time in seconds
0
30
60
90
120
150
180
210
240
270
300
a)
2.
Use information from the graph to calculate the halflife of this source.
A table of count rate (corrected for background) against time
is shown for a radioactive source.
Time/min
0
Corrected
Count Rate
in c.p.m.
500 300
a)
b)
5
10
15
20
25
30
200
150
80
50
22
Plot a graph to show these results.
Estimate the half life of the source from these results.
a)
b)
c)
4.
Count Rate in c.p.m.
88
72
60
52
44
39
36
34
32
29
30
Plot a graph to show these results.
Estimate the background count rate.
Estimate the half life of the source from these results.
Describe a method that could be used to measure the halflife of this radioactive source, using the apparatus shown.
You can ignore background radiation.