Happy Grove, Titchfield, Seaforth, St.
Mary High & Annotto Bay High School
Physics Tutorial – Section E
June 2009, Paper II, Question #1 – Section A
You must write your answers in the spaces provided in this booklet.
In determining the half-life of an alpha-emitting radioactive source, a student recorded the
following data in Table 1.
Table 1
Time, t / s Count Rate, R / s-1
0 100
50 76
100 62
150 47
200 37
250 29
a) Plot on graph paper, a graph of count rate, R versus time, t. (7 marks)
b) What is meant by the ‘half-life’ of a radioactive sample? (1 mark)
c) Describe the procedure a student would use to obtain the results in Table 1. State ONE
precaution. (3 marks)
d) i) From the graph, make TWO calculations of the half-life of the sample. (6 marks)
ii) From your results in d) i), calculate the mean (average) half-life. (2 mark)
e) Estimate the count rate of the sample after
i) 425 s
ii) 4 half-life periods (6 marks)
Total = 25 marks
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Mikhael V. Davis JP Revised: 5/28/2021
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Happy Grove, Titchfield, Seaforth, St. Mary High & Annotto Bay High School
Physics Tutorial – Section E
June 1987, Paper III, Question #7
a) Draw a diagram to represent the structure of a neutral helium atom. Clearly label the
components. Taking the mass of the smallest component to be 1 'unit', what are the approximate
masses of the other components? (8 marks)
X 234 4
b) U Th
90
+ 2
He
92
The equation above represents a nuclear decay.
i) What is the value of the mass number (represented by X) of the uranium?
234
ii) Write down the symbol for a nuclide which is an isotope of thorium - 234 ( Th)
90
iii) The thorium nuclide (Th) is not stable. It decays by (β-emission) to produce protactinium
(symbol Pa). Represent this reaction in an equation like the one above. (7 marks)
c) The half-life for the decay of Thorium-234 is 24 days. The Physics Department of the U.W.I,
in Jamaica bought a sample of this thorium from England. On the day of despatch its activity
was 4 x 105 Bq (i.e. 4 x 105 disintegrations per second).
i) What was the activity of the source when it arrived in Jamaica 72 days later?
ii)What safety precautions should the suppliers have taken to ensure that none of the dock
workers could be harmed? State any two. (5 marks)
Total 20 marks
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June 1993, Paper III, Question #4
a) Outline (i) the Rutherford model of the atom and (ii) the Thomson model of the atom. Explain
how the results of the Geiger-Marsden experiment supported only one of these two models.
(8 marks)
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Mikhael V. Davis JP Revised: 5/28/2021
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Happy Grove, Titchfield, Seaforth, St. Mary High & Annotto Bay High School
Physics Tutorial – Section E
b) Cobalt-60 ( Co)is one of the most widely used radio-isotopes in the treatment of cancer. It is
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formed from natural cobalt by the capture of a neutron and it has a half-life of 5.2 years. It
decays into Nickel (Ni) by the simultaneous emission of a beta particle and two gamma rays.
i) Which of the two emissions is more likely to be used in the treatment of cancer and why?
ii) Represent the formation and decay of cobalt-60 by two balanced nuclear equations.
iii) Determine the number of half-lives for cobalt-60 in a period of 26 years and hence calculate
how much of a 8 g sample of cobalt-60 will remain after this period. (12 marks)
Total = 15 marks
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June 1994, Paper II, Question #1
Table 1 below gives information related to part of a natural radioactive series. It shows that
Element A emits a beta particle and a gamma ray and changes to element B. Element B then
under goes a radioactive change to become Element C and so on.
Element Atomic Number Mass Number Radiation Emitted Half-Life
A 83 214 β, γ 20 minutes
B 84 214 1.6 x 10-4 seconds
C 82 210 19 years
D 83 210 5 days
E 84 210 β 138 days
F
Stable
a) What is a beta particle? (1 mark)
b) What is a gamma ray? (1 mark)
c) What are the atomic number and mass number of an alpha particle?
Mikhael V. Davis JP Revised: 5/28/2021
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Happy Grove, Titchfield, Seaforth, St. Mary High & Annotto Bay High School
Physics Tutorial – Section E
Atomic number: ________ Mass number: ________ (2 marks)
d) Name the radioactive emission when Element B changes to Element C, and Element C to
Element D.
B to C: ______________________ C to D: ______________________
(2 marks)
e) State the atomic number and mass number o Element F
Atomic number: ________ Mass number: ________ (2 marks)
f) How many protons and neutrons does the nucleus of Element D contain?
Protons: _________ Neutrons: _________ (2 marks)
g) Name a pair of elements in Table 1 that are ISOTOPES of the same element.
(1 mark)
h) Explain what is meant by the half–life of a radioactive isotope. (1 mark)
i) If the activity of a sample of Element D at a certain time is 600 emissions per second, calculate
the activity of the sample 15 days later. (3 marks)
Total = 15 marks
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June 2002 Paper II, Question #5
a) i) Draw a diagram showing the structure of the carbon atom 12C.
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(5 marks)
ii) Carbon-14 is often referred to as an isotope of carbon. Explain what is meant by the term
“isotope”. (1 mark)
b) Define 'half-life' when used in reference to a radio-active nuclide. (2 marks)
c) A radioactive tracer ha s a half-life of 18 hours. Calculate the fraction of the initial activity
remaining after 90 hours. (3 marks)
Mikhael V. Davis JP Revised: 5/28/2021
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Happy Grove, Titchfield, Seaforth, St. Mary High & Annotto Bay High School
Physics Tutorial – Section E
d) In a radioactive process the element Radium (Ra) emits gamma radiation and decays to Radon
(Rn) and Helium (He). The equation of this process is
226 A 4
Ra Rn + He
88 86 Z
Determine the values of A and Z. (4 marks)
Total = 15 marks
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January / June 2002 Paper III, Question #2 (Specimen Paper)
a) The Geiger-Marsden experiment (alpha-particle scattering experiment) supported a nuclear
model of the atom over the model that had been previously accepted. Briefly describe the model
which was accepted at the time of this experiment. Outline the Geiger-Marsden experiment and
show how the observations support the nuclear model. (8 marks)
b) i) A radioactive isotope of lead, Pb-214, emits beta-particles which a rate-meter detects. In
four consecutive periods, the number of counts recorded by the rate-meter was: 4823, 4764, 4829
and 4784. Explain why the count rate is not constant and find the average count.
ii) In a similar set of measurements 50 minutes later, the counts recorded were: 1216, 1169, 1225
and 1190. Find the average count at this time and use the two values you have calculated to find
the half-life of the source. (6 marks)
c) The proton number of lead is 82 and the product of the beta-decay of Pb-214 is bismuth (Bi).
Write down the nuclear reaction for this decay. Write down the symbol for another isotope of
lead and state the number of electrons a nuclear atom of this isotope would contain.
(6 marks)
Total 20 marks
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Mikhael V. Davis JP Revised: 5/28/2021
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Happy Grove, Titchfield, Seaforth, St. Mary High & Annotto Bay High School
Physics Tutorial – Section E
January / June Specimen Paper 2008, Paper II, Question #3
a) Complete the following table based on the structure of the atom.
Particle Symbol Polarity of Charge
Electron
Proton + ve
Neutron
Alpha
(7 marks)
b) A radioisotope Iodine-131, has a half life of 8 days. If administered to a patient, what fraction
of it will remain in the patient’s body after 24 days? (2 marks)
c) i) If the sun loses mass at a rate of 4.0 x 109 kg s-1, calculate the power of the sun.
(4 marks)
ii) The total power received by the earth’s surface is 1.79 x 1016 W. What portion of the total
power of the sun does this represents?
(Speed of light = 3.0 x 108 m s-1) (2 marks)
Total = 15 marks
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Mikhael V. Davis JP Revised: 5/28/2021
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