plumiActivity and half-life: OCR A‑Level Physics B questions
OCR A-Level Physics B past-paper questions on 6.2.2.4 Activity and half-life, 2016–2025, with mark schemes and examiner’s reports where available.
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Open the full PDFYour answerQ3(a)(i)
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Open the full PDFYour answerQ39(c)
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All 11 questions on Activity and half-life, as a list
- June 2025, Paper 1, Q28 (1 mark): An isotope emits alpha particles of energy 9.0 × 10–13 J. All of the alpha particles are absorbed by 0.25 kg tissue. The isotope gives a dose equivalent to 2.0
- June 2025, Paper 2, Q3(a)(i) (1 mark): Energy released in one decay of Pu‑238 = 8.96 × 10–13 J [1]
- June 2024, Paper 1, Q39(b) (4 marks): Thorium-232 is a radioactive metal that can be added to welding rods to improve their performance. These welding rods are said to be thoriated. Thorium-232 deca
- June 2022, Paper 1, Q12 (1 mark): A sample of a radioisotope has initial activity = A0. What is its activity after 0.5 half-lives? A 0.250 A0 B 0.293 A0 C 0.707 A0 D 0.750 A0 Your answer [1]
- June 2022, Paper 1, Q22 (1 mark): A radioactive source has a half-life of 27 days. The initial activity of the source is determined to be 2.5 × 104 Bq. How long will it take for the activity to
- June 2022, Paper 1, Q39(c) (4 marks): In a ‘thorium’ reactor, 234 92U is produced when a neutron is captured by a 233 92U nucleus. The 233 92U is produced from an isotope of thorium (Th) in the foll
- November 2021, Paper 1, Q34(a) (2 marks): Show that the number of atoms of 125I atoms initially present in one seed is about 6 × 1013. [2]
- November 2021, Paper 1, Q41(a)(iii) (2 marks): Estimate the number of neutrons that would decay in one second from a sample of 104 free neutrons. number per second = [2]
- November 2021, Paper 3, Q4(a)(iv) (1 mark): Krypton-81m has a half-life of only 13 seconds, whilst rubidium-81 has a half-life of 4 hours. Suggest why hospital stocks do not lose their activity before pat
- June 2018, Paper 2, Q3(a) (4 marks): An average banana contains about 5 × 10–4 kg of potassium. About 0.012% of this potassium is the beta-emitting isotope, potassium-40. Show that a single banana
- June 2018, Paper 3, Q2(b)(i) (2 marks): Explain what is meant by “Corrected count rate” and complete this column in the table. [2]
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