plumiRandom decay and half-life: Edexcel International A Level Physics questions
Edexcel International A Level Physics past-paper questions on 5.4.2.3 Random decay and half-life, 2019–2025, with mark schemes and examiner’s reports where available.
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Q20(b)(ii)
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All 33 questions on Random decay and half-life, as a list
- June 2025, Unit 5, Q20(b)(ii) (5 marks): When the space probe was launched, the decay of plutonium‑238 produced a power of 550 W. A website states that there was 1.00 kg of plutonium‑238 when the space
- June 2025, Unit 5, Q20(b)(iii) (2 marks): The space probe took 74 months to travel to Jupiter. Calculate the power produced when the space probe arrived at Jupiter, due to the decay of plutonium‑238. 1
- January 2025, Unit 5, Q21(a)(iii) (4 marks): In a particular paper mill, the Pm source was replaced when the activity of the source had decreased to 0.75% of its initial activity. Calculate the time that t
- October 2024, Unit 5, Q21(b) (4 marks): The half-life of uranium-241 is 40 minutes. The half‑life of uranium-242 is 17 minutes. Initially, a sample has the same number of uranium-241 atoms as uranium-
- June 2024, Unit 5, Q5 (1 mark): Which of the following correctly describes the random nature of radioactive decay? A Radioactive decay is a natural process. B Radioactive decay is a spontaneou
- June 2024, Unit 5, Q17(b)(i) (6 marks): For one treatment, the suggested activity to be used is 51.8 MBq kg –1. The mass of the patient is 65 kg. Calculate the mass of 131I required to treat this pati
- June 2024, Unit 5, Q17(b)(ii) (2 marks): For another treatment, a sample of 131I with an activity of 2.35 GBq is required. The sample is prepared 24 hours before it is required. Calculate the activity
- January 2024, Unit 5, Q5 (1 mark): Which of the following correctly describes the spontaneous nature of radioactive decay? A Radioactive decay is a natural process. B Radioactive decay is a rando
- January 2024, Unit 5, Q19(c)(ii) (3 marks): In Georgia, in December 2001, some men discovered two small canisters in a forest. The canisters were hot and had melted surrounding snow. The canisters 90Sr. w
- January 2024, Unit 5, Q19(c)(iii) (3 marks): The authorities claimed that the canisters were 50 years old. The activity of each 15 Bq. canister when new was 3.700 × 10 Assess the accuracy of the claim. 90S
- October 2023, Unit 5, Q19(a)(i) (2 marks): Show that the decay constant for caesium-137 is about 7.3 × 10 –10 s –1. half‑life of caesium-137 = 30.1 years 1 year = 3.15 × 10 7 s (2)
- October 2023, Unit 5, Q19(a)(ii) (3 marks): Calculate the mass of caesium in the capsule. (3) Mass of caesium =
- October 2023, Unit 5, Q19(a)(iii) (2 marks): Calculate the activity of the caesium in the capsule after 2 years. (2) Activity after 2 years =
- October 2023, Unit 5, Q19(b) (3 marks): The capsule was found after 14 days. Calculate the total energy, in J, released from the capsule in 14 days. activity of caesium in capsule = 19 GBq energy rele
- June 2023, Unit 5, Q16(b) (4 marks): Determine the time taken, in years, for 90% of the thorium-230 in a sample to decay to radium-226. half-life of thorium-230 = 75 400 years (4) Time taken = year
- January 2023, Unit 5, Q15(b) (4 marks): A sample of pure 137Cs has an activity of 7400 Bq. Calculate the mass, in kg, of the sample. half‑life of 137Cs = 30.2 years mass of 137Cs atom = 137 u 1 year =
- October 2022, Unit 5, Q5 (1 mark): The radioactive decay of a nucleus is described as a random process. Which of the following is a reason for this? A There are a number of different decay paths.
- October 2022, Unit 5, Q18(b) (4 marks): Radioactive phosphorus was one of the first artificially produced isotopes to be used in the diagnosis of cancerous tumours. The isotope 32P is injected into a
- October 2022, Unit 5, Q20(c)(i) (6 marks): A nuclear fission reactor produces about 24 kg of caesium-137 each year. A website states that 24 kg of caesium-137 has the same activity as 2000 kg of radium-2
- October 2022, Unit 5, Q20(c)(ii) (3 marks): Caesium-137 may enter plants grown in a contaminated area. The radiation from 100 g of plant material grown in a contaminated area can have a count rate as high
- June 2022, Unit 5, Q9 (1 mark): Bismuth decays to form a stable isotope of thallium. Which graph shows how the number N of thallium atoms in a sample of bismuth varies with time t? N N N N t t
- June 2022, Unit 5, Q13(c) (3 marks): A fertiliser contains potassium chloride. The activity of a sample of the fertiliser due to radioactive potassium was 48.6 Bq. It is claimed that the time t tak
- January 2022, Unit 5, Q4 (1 mark): Tritium is a radioactive isotope. Wine may contain traces of tritium. One 25‑year‑old bottle of wine was found to have an unusually high activity of 22 Bq. half
- January 2022, Unit 5, Q20(d) (4 marks): The activity of a sample of actinium‑225 is 7.4 × 107 Bq when it is prepared. Calculate the number of actinium atoms in the sample 7.0 days later. half‑life of
- January 2022, Unit 6, Q3(c) (2 marks): The corrected count rate C varies over time t according to the relationship C = C0 e−λt where C0 is the initial count rate and λ is the decay constant. Explain
- January 2022, Unit 6, Q3(d)(ii) (3 marks): Isotope X has a half-life of approximately 30 minutes. Determine a value of λ, in hours−1, for isotope Y. (3) λ = hours−1
- January 2022, Unit 6, Q3(d)(iii) (2 marks): Hence determine the half-life t½ for isotope Y. (2) t½ =
- October 2021, Unit 5, Q6 (1 mark): Polonium‑218 is a naturally occurring radioactive isotope with a half-life of 185 s. A sample of this isotope contains 2.75 × 1015 unstable nuclei. Which of the
- October 2021, Unit 5, Q19(b) (3 marks): The activity of a cobalt‑60 source is 4.07 × 1014 Bq initially. When used for sterilising, the source is replaced when the activity drops below 1.85 × 1014 Bq.
- June 2021, Unit 5, Q19(b) (5 marks): In one pacemaker, the activity of the plutonium source was measured to be 6.75 × 1010 Bq in 2020. Calculate the power of the source, in W, when it was fitted 40
- January 2021, Unit 5, Q19(b)(i) (3 marks): Show that the activity of this sample is about 1.9 ´ 105 Bq. (3)
- January 2021, Unit 5, Q19(b)(ii) (2 marks): It is claimed that after a period of 50 years, the activity of the sample would be less than the activity of a typical school source. Assess the validity of thi
- October 2020, Unit 5, Q18(c) (3 marks): The isotope Og-294 is extremely unstable and decays via alpha decay. After 2.5 ms, a sample contains 500 atoms of Og-294. Calculate the original number of Og-29
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