Half-life
5.2.5What the syllabus asks of you
- Define the half-life of a particular isotope as the time taken for half the nuclei of that isotope in any sample to decay; recall and use this definition in calculations, which may involve information in tables or decay curves
- Describe the dating of objects by the use of 14C
- Explain how the type of radiation emitted and the half-life of the isotope determine which isotope is used for applications including: (a) household fire (smoke) alarms (b) irradiating food to kill bacteria (c) sterilisation of equipment using gamma rays (d) measuring and controlling thicknesses of materials with the choice of radiations used linked to penetration and absorption (e) diagnosis and treatment of cancer using gamma rays
Read the notes first
Chapter 5: Half-life
Drill this topic
Every question on Half-life, untimed, marked as you go.
Make a worksheet
Choose the years and how many questions, then print it with the answers on separate pages.
26 questions
1May / June 2026 · Paper 11 · Q37Show mark scheme →
AThe isotope generates its own voltage.
BThe isotope has a long half-life.
CThe isotope is stable.
DThe isotope is dangerous to handle.
Mark scheme
2Oct / Nov 2025 · Paper 11 · Q37Show mark scheme →
Aalpha and gamma
Balpha only
Cbeta and gamma
Dbeta only
Mark scheme
3May / June 2025 · Paper 11 · Q37Show mark scheme →
A60 minutes
B80 minutes
C100 minutes
D160 minutes
Mark scheme
4May / June 2025 · Paper 12 · Q38Show mark scheme →
A6000 years
B18 000 years
C24 000 years
D96 000 years
Mark scheme
5Oct / Nov 2024 · Paper 12 · Q38Show mark scheme →
Aalpha particles, a few hours
Bbeta particles, a few years
Cgamma rays, a few hours
Dgamma rays, a few years
Mark scheme
6Oct / Nov 2023 · Paper 11 · Q38Show mark scheme →
AAfter 1.9 days there is 0.50 mg of radon-222 left.
BAfter 3.8 days there is 0.50 mg of radon-222 left.
CIts half-life is half that of a 2.0 mg sample.
DThere is no radon-222 left after 7.6 days.
Mark scheme
7Oct / Nov 2023 · Paper 12 · Q39Show mark scheme →
A75 µg
B80 µg
C210 µg
D560 µg
Mark scheme
8May / June 2023 · Paper 11 · Q37Show mark scheme →
AAlpha-particles are all stopped by the paper.
BAlpha-particles make the paper radioactive.
CGamma radiation is all stopped by the paper.
DGamma radiation is only produced by sources with a short half-life.
Mark scheme
9May / June 2023 · Paper 11 · Q38Show mark scheme →
A4.0 mg
B8.0 mg
C24 mg
D28 mg
Mark scheme
10May / June 2023 · Paper 12 · Q22Show mark scheme →
Aamericium-241, an alpha emitter with a half-life of 432 years
Bcobalt-60, a gamma emitter with a half-life of 5 years
Cradium-223, an alpha emitter with a half-life of 11 days
Dbarium-137, a gamma emitter with a half-life of 3 minutes
Mark scheme
11Oct / Nov 2022 · Paper 11 · Q39Show mark scheme →
Ahalf the time for all the unstable nuclei to decay
Bhalf the time it takes an unstable nucleus to emit radiation
Cthe time for half the unstable nuclei to decay
Dthe time for the nucleon number to halve
Mark scheme
12Oct / Nov 2022 · Paper 12 · Q40Show mark scheme →
A12C
B13C
C14C
D15C
Mark scheme
13Oct / Nov 2021 · Paper 11 · Q38Show mark scheme →
AIt has a long half-life and emits alpha radiation.
BIt has a long half-life and emits gamma radiation.
CIt has a short half-life and emits alpha radiation.
DIt has a short half-life and emits gamma radiation.
Mark scheme
14Oct / Nov 2021 · Paper 12 · Q38Show mark scheme →
Athe half-life of the isotope
Bthe mass of the sample
Cthe number of neutrons in the sample
Dthe rate of decay of the isotope
Mark scheme
15May / June 2021 · Paper 12 · Q40Also set in May / June 2021 Paper 11Show mark scheme →
A8 minutes
B9 minutes
C18 minutes
D24 minutes
Mark scheme
16Oct / Nov 2020 · Paper 11 · Q40Show mark scheme →
A7.0 years
B14 years
C21 years
D28 years
Mark scheme
17Oct / Nov 2020 · Paper 12 · Q39Show mark scheme →
Ahalf of the time it takes for one atom to decay
Bhalf of the time taken for all the atoms in a sample to decay
Cthe time taken for half of the atoms in a sample to decay
Dthe time taken for the nucleon number (mass number) to halve
Mark scheme
18May / June 2020 · Paper 11 · Q38Show mark scheme →
Acooking meals
Bdiagnosing illnesses
Csterilising equipment
Dtreating illnesses
Mark scheme
19May / June 2020 · Paper 11 · Q39Show mark scheme →
A5700 years
B11 400 years
C17 100 years
D22 800 years
Mark scheme
20Oct / Nov 2019 · Paper 12 · Q39Show mark scheme →
Aan alpha-particle emitter with a half-life of a few hours
Ban alpha-particle emitter with a half-life of a few years
Ca gamma ray emitter with a half-life of a few hours
Da gamma ray emitter with a half-life of a few years
Mark scheme
21May / June 2018 · Paper 11 · Q36Show mark scheme →
Abeta, 1 hour
Bbeta, 6 years
Cgamma, 1 hour
Dgamma, 6 years
Mark scheme
22May / June 2018 · Paper 11 · Q38Show mark scheme →
A20 million
B10 million
C5 million
Dzero
Mark scheme
23Oct / Nov 2017 · Paper 12 · Q37Show mark scheme →
Athe mass of the sample
Bthe nucleon (mass) number
Cthe number of atoms of the isotope
Dthe proton (atomic) number
Mark scheme
24Oct / Nov 2016 · Paper 12 · Q39Also set in Oct / Nov 2016 Paper 11Show mark scheme →
A4.0 days
B5.0 days
C20 days
D80 days
Mark scheme
25May / June 2016 · Paper 11 · Q39Show mark scheme →
A2500 counts per minute
B5000 counts per minute
C20 000 counts per minute
D40 000 counts per minute
Mark scheme
26May / June 2016 · Paper 12 · Q39Show mark scheme →
AHalf-life changes as the isotope decays.
BHalf-life is the time it takes for the nucleon number of the isotope to halve.
CHalf-life is half the time it takes for the number of nuclei of the isotope to decrease to zero.
DHalf-life is the time it takes for the number of nuclei of the isotope to decrease by half.
Mark scheme