Half-life: past paper questions

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• Question 37May/June 2026, paper 11Multiple choice1 mark

  Most household smoke detectors contain a sample of an isotope of americium. The battery in a smoke detector is replaced very frequently, but the sample of the isotope of americium does not need to be replaced. Why does the americium isotope not need to be replaced?

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• Question 37May/June 2025, paper 11Multiple choice1 markHas a diagram

  The graph shows the results of an experiment to measure the count rate of a radioactive isotope. What is the half-life of the isotope?

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• Question 38Oct/Nov 2023, paper 11Multiple choice1 mark

  The isotope radon-222 has a half-life of $3.8\text{ days}$. Which statement about a sample containing $1.0\text{ mg}$ of radon-222 is correct?

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• Question 8May/June 2026, paper 22Structured10 marksHas a diagram

  The isotope iodine-131 is used in the treatment of cancer. During treatment, iodine-131 is absorbed by the cancer cells. Beta particles emitted from iodine-131 destroy the cancer cells.

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• Question 38May/June 2025, paper 12Multiple choice1 mark

  An isotope has a half-life of $6000\text{ years}$. How much time passes before the count rate due to emissions from a sample of the isotope decreases to $\frac{1}{16}$ of the initial value?

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• Question 8Oct/Nov 2024, paper 21Structured8 marks

  The nuclide notation for the radioactive isotope hydrogen-3 is ${}_1^3\text{H}$. Explain why hydrogen-3 cannot decay by the emission of alpha particles.

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• Question 39Oct/Nov 2023, paper 12Multiple choice1 mark

  The half-life of a radioactive isotope is $2.5\text{ minutes}$. This isotope is the only radioactive isotope in a radioactive sample. Between time $t=0$ and $t=7.5\text{ minutes}$, the mass of this isotope in the sample decreases by $70\mu \text{g}$.

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• Question 8Oct/Nov 2024, paper 22Structured9 marksHas a diagram

  The isotope thorium-230 (${}_{90}^{230}\text{Th}$) decays by alpha particle ($\alpha$-particle) emission. Describe the composition of an $\alpha$-particle.

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• Question 9May/June 2024, paper 22Structured9 marks

  Alpha particles are sometimes emitted from the nuclei of radioactive elements. This emission is both random and spontaneous. Describe what is meant by ‘spontaneous’ emission.

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• Question 22May/June 2023, paper 12Multiple choice1 mark

  Which radioactive isotope can be used for measuring cracks or flaws in metal components?

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• Question 10May/June 2023, paper 21Structured8 marksHas a diagram

  Carbon-14 is an isotope of carbon. It undergoes radioactive decay with a half-life of 6000 years. The age of a sample of wood is found using the carbon-14 that it contains.

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