Topic 12 Practice Paper: Nuclear physics — question paper (print)

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IGCSE · Cambridge IGCSE Physics (Extended (Core + Supplement))

Topic 12 Practice Paper

Nuclear physics

Duration: 40 minutes

Total: 30 marks

Name:

Class:

Date:

READ THESE INSTRUCTIONS FIRST

Answer all questions.
Section A contains ten multiple-choice questions. Choose one answer, A, B, C or D, for each.
Section B contains structured questions. Write your answers in the spaces provided.
The number of marks is given in brackets [ ] at the end of each question or part question.
The total mark for this paper is 30.

Original practice material written against the Cambridge IGCSE Physics syllabus. It is not an official Cambridge examination paper. Topic 12: Nuclear physics (nuclear atom, background, α/β/γ, decay equations, half-life, safety).

For Examiner’s Use
Section A	/ 10
Section B	/ 20
Total	/ 30

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

1
Which row gives the relative charges of the proton, neutron and electron?
Proton Neutron Electron
A 0 +1 −1
B +1 0 −1
C +1 −1 0
D −1 0 +1
2
The nuclide ¹⁴₆C contains
1. A14 neutrons and 6 protons
2. B6 neutrons and 14 protons
3. C8 neutrons and 6 protons
4. D6 neutrons and 8 protons
( )
3
The alpha-scattering experiment showed that most alpha particles passed straight through thin gold foil. This is evidence that atoms contain
1. Amostly empty space
2. Bno electrons
3. Clarge solid nuclei
4. Dmore protons than neutrons
( )
4
Which list contains only sources of background radiation?
1. AMicrowave ovens, power lines, mobile phones
2. BRadon gas, cosmic rays, food and drink
3. CX-ray machines, lasers, lamps
4. DCar exhausts, sea water, wind
( )
5
Radiation that is weakly ionising but penetrates several centimetres of lead is
1. Aalpha
2. Bbeta
3. Cultrasound
4. Dgamma
( )
6
Radioactive decay is described as spontaneous and random. This means
1. Athe nucleus decays when the sample is heated
2. Bthe count rate is always constant
3. Cthe decay happens by itself, in an unpredictable direction and at an unpredictable moment
4. Dthe half-life can be changed by cooling
( )
7
Carbon-14 (¹⁴₆C) decays by beta emission. The daughter nucleus is
1. A¹⁴₇N
2. B¹⁴₅B
3. C¹⁰₇N
4. D¹⁴₆C
( )
8
In beta-minus decay the proton number of the nucleus
1. Afalls by 1
2. Bstays the same
3. Crises by 4
4. Drises by 1
( )
9
A source has a half-life of 5.0 years. What fraction of the original nuclei remains after 15 years?
1. Aone half
2. Bone eighth
3. Cone quarter
4. Done sixteenth
( )
10
Radioactive sources are stored in lead-lined boxes mainly to
1. Akeep them warm
2. Bprevent the sources decaying
3. Cabsorb the radiation so people nearby are protected
4. Dmake the sources last longer
( )

	Proton	Neutron	Electron
A	0	+1	−1
B	+1	0	−1
C	+1	−1	0
D	−1	0	+1

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

11
Alpha particles were fired at a very thin sheet of gold foil. Most passed straight through; a few deflected through large angles; about 1 in 8000 bounced straight back.
1. (a)
  State what the straight-through majority shows about the atom.
  [1]
2. (b)
  State what the large-angle deflections show about the nucleus.
  [2]
3. (c)
  State what the rare bounce-backs show about the nucleus’s mass.
  [1]
4. (d)
  State the charge and composition of an alpha particle.
  [2]
12
A nucleus of ²³⁸₉₂U (uranium) decays by alpha emission, and the daughter nucleus then decays by beta emission.
1. (a)
  Write the equation for the alpha decay of ²³⁸₉₂U, naming thorium (Th, Z = 90) as the daughter.
  [2]
2. (b)
  Write the equation for the beta decay of the thorium daughter (the product is protactinium, Pa, Z = 91).
  [2]
3. (c)
  Explain, in terms of particles inside the nucleus, what happened during the beta decay.
  [2]
13
A source has a half-life of 20 minutes. A detector reading near it is 1320 counts/min, and the background count rate is 40 counts/min.
1. (a)
  Work out the count rate due to the source alone at the start.
  [1]
2. (b)
  Use the half-life to find the source count rate one hour later.
  [2]
3. (c)
  State the number the meter would actually display after one hour.
  [2]
14
A laboratory technician handles a strong gamma source for measurements several times each week.
1. (a)
  State two effects ionising radiation can have on living cells.
  [1]
2. (b)
  Describe three precautions the technician should take while using the source.
  [2]

— End of paper —