Physics 9702 · AS & A Level
Radioactive decay
57 practice questions on Radioactive decay, with worked solutions and instant marking.
Beryllium-7 ($^{7}_{4}\text{Be}$) forms in the upper atmosphere and then falls to the Earth’s surface. Beryllium-7 nuclei decay with a half-life of 53.3 days, producing stable nuclei. A sample of beryllium-7 on a tree leaf has an activity of $39\,\text{mBq}$.
Feb/March 2016
Define the radioactive decay constant.
Feb/March 2018
State what spontaneous decay means.
Feb/March 2021
Polonium-211 ($^{211}_{84}\text{Po}$) undergoes alpha emission, forming a stable lead (Pb) isotope.
Feb/March 2022
Polonium-193 $^{193}_{84}\text{Po}$ is an unstable nuclide. A nucleus of polonium-193 undergoes decay into a nucleus of lead-189 $^{189}_{82}\text{Pb}$ by emitting an alpha-particle.
Feb/March 2025
Americium-241 is a radioactive element made artificially and it emits $\alpha$-particles. A sample of americium-241 with mass $5.1\,\mu\text{g}$ is measured to have an activity of $5.9 \times 10^5\,\text{Bq}$.
May/June 2010
Americium-241 is a radioactive element made artificially, and it gives off $\alpha$-particles. A sample of americium-241 with mass $5.1\,\mu\text{g}$ is measured to have an activity of $5.9 \times 10^{5}\,\text{Bq}$.
May/June 2010
State what the decay constant of a radioactive isotope means.
May/June 2012
Strontium is known to have at least 16 isotopes. Strontium-89 is one of them. Its half-life is 52 days.
May/June 2012
State the meaning of the decay constant of a radioactive isotope.
May/June 2012
Some of the water is polluted with radioactive iodine-131 ($^{131}_{53}\text{I}$). The activity of the iodine-131 in $1.0\,\text{kg}$ of this water is $460\,\text{Bq}$. Iodine-131 has a half-life of $8.1\,\text{days}$.
May/June 2014
An isotope of an element is radioactive. Explain what radioactive decay means.
May/June 2015
The power for a space probe is to come from the energy released when plutonium-236 decays through emission of $\alpha$-particles. Each $\alpha$-particle has energy $5.75\,\text{MeV}$, and their energy is collected and turned into electrical energy with an efficiency of $24\%$.
May/June 2015
An isotope of an element is radioactive. Explain what radioactive decay means.
May/June 2015
Copper-66 is a radioactive isotope. As a nucleus of copper-66 decays, the emitted radiation includes a $\beta^-$ particle and a $\gamma$-ray photon. The count rate from a sample of copper-66 is determined with a detector and counter, as shown in Fig. 13.1.
May/June 2016
What is meant by gamma radiation ($\gamma$-radiation)?
May/June 2016
Copper-66 is a radioactive isotope. When a copper-66 nucleus undergoes decay, the emissions include a $\beta^-$ particle and a $\gamma$-ray photon. The count rate from a sample of the isotope copper-66 is recorded with a detector and counter, as shown in Fig. 13.1.
May/June 2016
State the meaning of radioactive decay.
May/June 2018
State what radioactive decay means.
May/June 2018
State what the term radioactive decay means.
May/June 2018
A radioactive isotope sample has $N$ nuclei present at time $T$. By time $(T + \Delta T)$, it contains $(N - \Delta N)$ nuclei. The interval $\Delta T$ is short.
May/June 2019
A sample containing a radioactive isotope has $N$ nuclei of the isotope at time $T$. By time $(T + \Delta T)$, it contains $(N - \Delta N)$ nuclei of the isotope. The interval $\Delta T$ is short.
May/June 2019
A sample of a radioactive isotope is described as having random and spontaneous decay. Explain what is meant by the decay being random.
May/June 2020
A sample of a radioactive isotope is described as random and spontaneous. Explain what is meant by the decay being random.
May/June 2020
State what the term radioactive decay means.
May/June 2022
Carbon-11 is radioactive and undergoes $\beta^+$ emission to produce boron-11. The half-life of Carbon-11 is $20$ minutes. Boron-11 is stable.
May/June 2023
Carbon-11 is a radioactive isotope that decays by $\beta^+$ emission, producing boron-11. The half-life of carbon-11 is 20 minutes. Boron-11 is stable.
May/June 2023
What is the definition of the half-life of a radioactive isotope?
May/June 2024
Define the half-life of a radioactive isotope.
May/June 2024
Define the activity of a radioactive sample.
May/June 2025
Radioactive decay is a spontaneous process. State what the term spontaneous means in this context.
May/June 2025
Define activity of a radioactive sample in terms of its decay rate.
May/June 2025
Phosphorus-33 ($^{33}_{15}\text{P}$) is a radioactive isotope that decays by $\beta$-decay into stable sulfur-33 ($^{33}_{16}\text{S}$). Its half-life is $24.8$ days.
Oct/Nov 2011
Phosphorus-33, $^{33}_{15}\text{P}$, decays by $\beta$-emission into stable sulfur-33, $^{33}_{16}\text{S}$. Its half-life is $24.8\,\text{days}$.
Oct/Nov 2011
Radon-222 has a half-life of 3.82 days and is a radioactive element. If radon-222 is present in atmospheric air, it can be a health hazard. Safety measures ought to be taken whenever the activity of radon-222 is above 200 Bq per cubic metre of air.
Oct/Nov 2011
A possible nuclear fission equation is $^{235}_{92}\text{U} + ^{1}_{0}\text{n} \rightarrow ^{141}_{56}\text{Ba} + ^{92}_{36}\text{Kr} + 3^{1}_{0}\text{n} + \text{energy}$. Barium-141 ($^{141}_{56}\text{Ba}$) together with krypton-92 ($^{92}_{36}\text{Kr}$) are both $\beta$-emitters. Barium-141 has a half-life of 18 minutes and a decay constant of $6.4 \times 10^{-4}\,\text{s}^{-1}$. Krypton-92 has a half-life of 3.0 seconds.
Oct/Nov 2013
At the point of nuclear reactor decommissioning, a steel mass of $2.5 \times 10^{6}\,\text{kg}$ is discovered to be polluted by radioactive nickel-63 ($^{63}_{28}\text{Ni}$). The steel’s total activity arising from the nickel-63 contamination is $1.7 \times 10^{14}\,\text{Bq}$.
Oct/Nov 2014
Distinguish, for an atom, the nucleus from a nucleon.
Oct/Nov 2015
Distinguish, for an atom, between a nucleus and a nucleon.
Oct/Nov 2015
State the meaning of the binding energy of a nucleus.
Oct/Nov 2015
Radon-222 ($^{222}_{86}\text{Rn}$) is a radioactive element present in atmospheric air. Its decay constant is $2.1 \times 10^{-6}\,\text{s}^{-1}$.
Oct/Nov 2016
Radon-222 ($^{222}_{86}\text{Rn}$) is a radioactive element present in atmospheric air. Its decay constant is $2.1 \times 10^{-6}\,\text{s}^{-1}$.
Oct/Nov 2016
A radiation detector is set near to a radioactive source. The detector does not enclose the source. Radiation is emitted in all directions and, because of this, the activity of the source and the measured count rate are not the same. Suggest two other reasons why the activity and the measured count rate may differ.
Oct/Nov 2017
Iodine-131 ($^{131}_{53}\text{I}$) is a radioactive isotope with decay constant $8.6 \times 10^{-2}\,\text{day}^{-1}$. The $\beta^{-}$ particles it emits have a maximum energy of $0.61\,\text{MeV}$.
Oct/Nov 2017
A radiation detector is placed near a radioactive source, but it does not enclose the source. Since radiation leaves the source in all directions, the source activity and the measured count rate are not the same. Suggest two further reasons why these two quantities may differ.
Oct/Nov 2017
What does radioactive decay mean?
Oct/Nov 2018
State what radioactive decay means.
Oct/Nov 2018
Radon-222 ($^{222}_{86}\text{Ra}$) is a radioactive gas whose decay is random, with decay constant of $7.55 \times 10^{-3}\,\text{hour}^{-1}$.
Oct/Nov 2019
Iodine-131 $\left(^{131}_{53}\text{I}\right)$ is a radioactive isotope, and its decay constant is $9.9 \times 10^{-7}\text{ s}^{-1}$.
Oct/Nov 2020
Iodine-131 $^{131}_{53}\text{I}$ is a radioactive isotope that has a decay constant equal to $9.9 \times 10^{-7}\,\text{s}^{-1}$.
Oct/Nov 2020
This question is about radioactive decay.
Oct/Nov 2021
Radioactive decay is both random and spontaneous. State the meaning of random.
Oct/Nov 2021
This question is about radioactive decay.
Oct/Nov 2021
Carbon-15 ($^{15}_{6}\text{C}$) is a carbon isotope that decays radioactively into nitrogen-15 ($^{15}_{7}\text{N}$), which is a stable nitrogen isotope. Radioactive decay is both random and spontaneous.
Oct/Nov 2022
Carbon-15 $\left(^{15}_{6}\text{C}\right)$ is a carbon isotope that decays radioactively into nitrogen-15 $\left(^{15}_{7}\text{N}\right)$, a stable isotope of nitrogen. Radioactive decay is both a random process and a spontaneous process.
Oct/Nov 2022
Radioactive decay is both random and spontaneous. State what is meant by random in this context.
Oct/Nov 2024
Oxygen-15 $\left(^{15}_{8}\mathrm{O}\right)$ is radioactive and has a half-life of 2.04 minutes. When oxygen-15 decays, positrons are produced. Because of this, oxygen-15 is sometimes used as a tracer in positron emission tomography (PET scanning).
Oct/Nov 2025