Edexcel IGCSE Physics B Radioactivity Questions

Practise explaining nuclei, isotopes, ionising radiation, nuclear decay, penetration tests, detectors and count-rate calculations.

Exam points

interpret proton, neutron and electron information for atoms, ions and isotopes
complete nuclear decay equations by balancing atomic and mass numbers
use detector readings to correct for background count and estimate activity in Bq

Covered syllabus points

7.2 Atomic structure and nuclei 7.3 Atomic number, mass number and isotopes 7.4 Ionising radiation 7.5 Alpha, beta and gamma radiation 7.6 Radiation penetration practical 7.7 Nuclear emission effects 7.8 Balancing nuclear equations 7.9 Detecting ionising radiation 7.10 Background radiation 7.11 Radioactive activity 7.12 Half-life 7.13 Half-life calculations 7.14 Uses of radioactivity 7.15 Contamination and irradiation 7.16 Dangers of ionising radiation

[Maximum number: 6]

(a)

Which statement describes the term atomic number for a nucleus?

number of electrons in the nucleus

number of neutrons in the nucleus

number of protons in the nucleus

number of protons and neutrons in the nucleus

[ 1 ]

(b)

Which statement describes the term mass number for a nucleus?

number of electrons in the nucleus

number of neutrons in the nucleus

number of protons in the nucleus

number of protons and neutrons in the nucleus

[ 1 ]

(c)

Which statement describes the term isotopes?

atoms with the same number of electrons but a different number of protons

atoms with the same number of neutrons but a different number of electrons

atoms with the same number of neutrons but a different number of protons

atoms with the same number of protons but a different number of neutrons

[ 1 ]

(d)

An atom contains 8 protons, 8 neutrons and 8 electrons.

Which of these would result in a negatively charged ion of the same element?

adding an electron

adding a proton

removing an electron

removing a proton

[ 1 ]

(e)

It is not possible to predict exactly when a radioactive nucleus will decay.

Which feature of radioactive decay best explains this observation?

radioactive decay can change the structure of the nucleus

radioactive decay happens at random

radioactive decay is irreversible

radioactive decay makes a nucleus more stable

[ 1 ]

(f)

Which of these is the correct unit for measuring the activity of a radioactive sample?

becquerel (Bq)

coulomb (C)

joule (J)

watt (W)

[ 1 ]

[Maximum number: 13]

This question is about radioactive isotopes used for medical imaging.

(a)

lodine-131 is represented by this symbol.

{ }_{53}^{131} \mathrm{I}

[ 8 ]

(i)

How many neutrons are in the nucleus of an atom of iodine-131?

131

184

[ 1 ]

(ii)

Iodine-131 is radioactive and decays with a half-life of 8 days.

State what is meant by the term half-life.

[ 2 ]

(iii)

The cross ( x ) on the graph shows the initial number of atoms in a sample of iodine-131.

Draw three more crosses ( × ) on the graph to show how the number of atoms of iodine-131 in the sample changes during three half-lives.
[iodine-131 half-life =8 days]

Figure for Question (iii) — Edexcel IGCSE Physics

[ 3 ]

(iv)

Use a curve of best fit on the graph to estimate the time taken for the number of atoms in the sample to decrease to 5000.
time taken = days

[ 2 ]

(b)

When iodine-131 decays, it emits beta radiation and gamma radiation.

A patient swallows a tablet containing iodine-131. The radiation emitted can be detected outside the body.

[ 2 ]

(i)

State the name of a piece of equipment that can detect the radiation emitted by iodine-131.

[ 1 ]

(ii)

Give a reason why gamma radiation is more likely to be detected outside the body than beta radiation.

[ 1 ]

(c)

Technetium-99m is another radioactive isotope.

Iodine-131 and technetium-99m are both used as medical tracers. Medical tracers use radiation detected outside the body to diagnose illnesses.

The table gives information about some of the properties of iodine-131 and technetium-99m when they undergo radioactive decay.

Table for Question (c) — Edexcel IGCSE Physics

Explain why technetium-99m is likely to be safer than iodine-131 when used as a medical tracer.

[ 3 ]

[Maximum number: 10]

A teacher investigates the penetrating ability of the gamma rays from a gamma source.
This is the teacher's method.
- place the gamma source at a distance of 25 cm from a radiation detector
- place a 1 cm thick absorbing material between the source and the detector
- measure the radiation count from the source for a time period of 3 s
- calculate the count rate in counts per second
- repeat the measurement two more times

The teacher repeats this method for different absorbing materials.

(a)

Name a suitable radiation detector that the teacher could use.

[ 1 ]

(b)

State the independent variable in the teacher's investigation.

[ 1 ]

(c)

Explain why every absorbing material used in the investigation has a thickness of 1 cm .

[ 2 ]

(d)

Suggest one improvement the teacher could make to this method.

[ 1 ]

(e)

The table shows the teacher's results for seven different absorbing materials.

Table for Question (e) — Edexcel IGCSE Physics

[ 5 ]

(i)

On the grid, plot a bar chart of the mean count rate for each absorbing material.

Figure for Question (i) — Edexcel IGCSE Physics

[ 3 ]

(ii)

A student concludes that plastic is the best absorber of gamma radiation because plastic gives the largest mean count rate.

Evaluate the student's conclusion.

[ 2 ]

[Maximum number: 1]

An atom contains 8 protons, 8 neutrons and 8 electrons.

Which of these would result in a negatively charged ion of the same element?

adding an electron

adding a proton

removing an electron

removing a proton

[Maximum number: 1]

This question is about radioactive isotopes used for medical imaging.

lodine-131 is represented by this symbol.

{ }_{53}^{131} \mathrm{I}

How many neutrons are in the nucleus of an atom of iodine-131?

131

184

[Maximum number: 1]

It is not possible to predict exactly when a radioactive nucleus will decay.

Which feature of radioactive decay best explains this observation?

radioactive decay can change the structure of the nucleus

radioactive decay happens at random

radioactive decay is irreversible

radioactive decay makes a nucleus more stable

[Maximum number: 1]

This question is about radioactive isotopes used for medical imaging.

When iodine-131 decays, it emits beta radiation and gamma radiation.

A patient swallows a tablet containing iodine-131. The radiation emitted can be detected outside the body.

Give a reason why gamma radiation is more likely to be detected outside the body than beta radiation.

[Maximum number: 2]

This question is about using carbon dating to find the age of pieces of wood.

The equation shows how carbon-14 forms in the atmosphere.

{ }_{0}^{1} \mathrm{n}+{ }_{7}^{14} \mathrm{~N} \rightarrow{ }_{6}^{14} \mathrm{C}+{ }_{1}^{1} \mathrm{X}

Carbon-14 decays by beta decay.

State what happens to the number of protons and the number of neutrons in a carbon-14 nucleus when it decays.

[Maximum number: 2]

Figure for Question 9 — Edexcel IGCSE Physics

Calculate x, the number of neutrons released by this fission reaction.

x = ............

[Maximum number: 1]

This question is about radioactive isotopes used for medical imaging.

When iodine-131 decays, it emits beta radiation and gamma radiation.

A patient swallows a tablet containing iodine-131. The radiation emitted can be detected outside the body.

State the name of a piece of equipment that can detect the radiation emitted by iodine-131.

[Maximum number: 1]

A material called granite is used as a work surface in a kitchen.

Figure for Question 11 — Edexcel IGCSE Physics

Granite is formed naturally and contains radioactive isotopes.

The granite work surface contributes to the background radiation in the kitchen.
Give another naturally occurring source of background radiation.

[Maximum number: 1]

Which of these is the correct unit for measuring the activity of a radioactive sample?

becquerel (Bq)

coulomb (C)

joule (J)

watt (W)

[Maximum number: 2]

This question is about radioactive isotopes used for medical imaging.

lodine-131 is represented by this symbol.

{ }_{53}^{131} \mathrm{I}

Iodine-131 is radioactive and decays with a half-life of 8 days.

State what is meant by the term half-life.

[Maximum number: 3]

This question is about radioactive isotopes used for medical imaging.

Table for Question 14 — Edexcel IGCSE Physics

Explain why technetium-99m is likely to be safer than iodine-131 when used as a medical tracer.

[Maximum number: 2]

Some of the energy stored in the nuclei of atoms can be used to generate electricity.

A nuclear fission power station generates electricity.

The daughter nuclei can cause contamination and irradiation.

Describe the difference between contamination and irradiation.

[Maximum number: 5]

Some radioactive waste from nuclear power stations has a very long half-life.

Discuss precautions that must be taken when disposing of this radioactive waste.

All question bank results loaded

Covered syllabus points

Question 1

Question (a)

Question (b)

Question (c)

Question (d)

Question (e)

Question (f)

Question 2

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (iv)

Question (b)

Question (i)

Question (ii)

Question (c)

Question 3

Question (a)

Question (b)

Question (c)

Question (d)

Question (e)

Question (i)

Question (ii)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16