Nuclear PhysicsCambridge IGCSE Physics: Topic test

20 questions, 54 marks

Cambridge IGCSE Physics

Nuclear Physics topic test

Total 54 marks

Name

Class

Date

1
An atom of chlorine has a proton number of 17 and a nucleon number of 35. A student writes the nuclide notation for this atom and then considers how it could form a chloride ion by gaining one electron.
(a)
How many neutrons does this atom of chlorine have?
[1 mark]
A17
B18
C35
D52
(b)
Which row correctly gives the number of protons and electrons in a chloride ion, Cl-, formed when this atom gains one electron?
[1 mark]
A17 protons, 17 electrons
B18 protons, 18 electrons
C17 protons, 16 electrons
D17 protons, 18 electrons
(c)
Describe the structure of this chlorine atom in terms of the nucleus and the electrons, and state the overall charge of a neutral atom.
[2 marks]
Total for question 1: 4 marks
2
A research reactor fuses two hydrogen-2 (deuterium) nuclei, each with a proton number of 1 and a nucleon number of 2, to form a single helium-3 nucleus and a free neutron.
(a)
What is the nucleon number of the neutron released, given that the total nucleon number must be conserved and the helium nucleus formed has a nucleon number of 3?
[1 mark]
A1
B2
C3
D4
(b)
What is the proton number of the helium nucleus formed, given that the two deuterium nuclei together have a proton number of 1 each and no protons are lost or gained in the fusion?
[1 mark]
A1
B2
C3
D4
(c)
State what is meant by nuclear fusion, and explain in terms of energy why this reaction releases energy rather than absorbing it.
[2 marks]
Total for question 2: 4 marks
3
A student places a small sealed radioactive source close to a Geiger-Muller tube connected to a ratemeter, and measures the corrected count rate with no absorber present, then with a sheet of paper between the source and the tube, and then with a 5 mm sheet of aluminium in place of the paper. The corrected count rate decreases substantially when the paper is added, and decreases further, but far less sharply, when the aluminium is used instead.
(a)
Using the changes in count rate described, identify the type(s) of nuclear radiation that must be present in the emission from this source, and explain your reasoning.
[3 marks]
(b)
The student then repeats the measurement with a thick sheet of lead in place of the aluminium, and finds that a small count rate remains, higher than the background count rate recorded with no source present. Explain what this final observation shows, and describe how the student should use the background measurement to find the true count rate due to the source in each case.
[4 marks]
Total for question 3: 7 marks
4
A sample contains the radioactive isotope strontium-90, which decays by beta emission to form yttrium-90 and has a half-life of 28 years. Strontium has a proton number of 38 and yttrium has a proton number of 39. A sample of strontium-90 initially has an activity of 800 MBq.
(a)
Write a balanced nuclide equation for the beta decay of strontium-90 to yttrium-90, using nuclide notation of the form ^A_Z X for each particle, and explain, in terms of the changes inside the nucleus, why a beta particle is emitted and why the proton number increases by one during this decay.
[6 marks]
(b)
The initial activity of the sample is 800 MBq. Calculate the activity of the sample after 84 years, showing your working, and explain what is meant by the half-life of an isotope.
[6 marks]
Total for question 4: 12 marks
5
An atom of magnesium has 12 protons, 12 neutrons and 12 electrons. It reacts to form a magnesium ion, Mg2+, by losing two electrons.
(a)
What is the nucleon number of this magnesium atom?
[1 mark]
A12
B13
C24
D36
(b)
How many electrons does the magnesium ion, Mg2+, have?
[1 mark]
A10
B12
C14
D24
(c)
Explain, in terms of protons and electrons, why the magnesium ion Mg2+ has an overall positive charge.
[2 marks]
Total for question 5: 4 marks
6
A physics class studies a nuclear fission reaction in which a uranium-235 nucleus (proton number 92) absorbs a neutron and splits into a strontium nucleus (nucleon number 94, proton number 38), a xenon nucleus, and two neutrons. The total nucleon number before the reaction is 236.
(a)
What is the proton number of the xenon nucleus produced, given that the total proton number must be conserved?
[1 mark]
A38
B54
C56
D92
(b)
What is the nucleon number of the xenon nucleus, given that the total nucleon number before the reaction is 236 and the strontium nucleus has a nucleon number of 94?
[1 mark]
A94
B138
C140
D142
(c)
State what is meant by nuclear fission, and identify one particle, other than the strontium and xenon nuclei, that this reaction releases.
[2 marks]
Total for question 6: 4 marks
7
A technician uses a Geiger-Muller tube and counter to investigate an unlabelled sealed source in a school store cupboard. With no absorber present the corrected count rate is 640 counts/minute. Placing a thick sheet of paper between the source and the tube reduces the corrected count rate only slightly, to 610 counts/minute, and placing a 2 cm thick sheet of lead between the source and the tube reduces the corrected count rate further, to 25 counts/minute, though it does not fall to zero.
(a)
Using this information, deduce which type or types of nuclear radiation the source could be emitting, giving a reason for each conclusion.
[3 marks]
(b)
Suggest why it is important for the technician to compare each reading with the corrected count rate, rather than the raw reading from the counter, describing how the corrected count rate is obtained, and state one precaution the technician should take while handling this source.
[4 marks]
Total for question 7: 7 marks
8
An industrial company owns a small sealed source of cobalt-60, used to calibrate detection equipment in a workshop. The source emits gamma radiation, has a half-life of 5.3 years, and has an initial activity of 640 kBq. It must be stored securely when not in use.
(a)
Calculate how long it takes for the activity of this cobalt-60 source to fall from 640 kBq to 40 kBq, showing your working, and explain what your answer means in terms of the fraction of radioactive nuclei remaining undecayed in the source.
[6 marks]
(b)
Explain three separate precautions the company should take to reduce the radiation dose received by workers who use this source, referring in each case to how the precaution reduces the dose, and explain why gamma-emitting sources such as this one require different shielding from a source that only emits alpha radiation.
[6 marks]
Total for question 8: 12 marks

End of questions