23. Nuclear physics
A section of Physics, 9702
Listing 10 of 119 questions
Radioactive decay is both random and spontaneous. State what is meant by: random spontaneous. A sample of radioactive material contains atoms of an unstable nuclide X. The activity of the sample due to the atoms of X is A. The variation with time t of ln A is shown in . 35.00 35.4 35.8 36.2 36.6 In (A / Bq) t / min Use to determine the half-life, in minutes, of nuclide X. half-life = min At time t = 0, the mass of the atoms of X in the sample is 5.66 × 10–7 kg. Determine the nucleon number of X. nucleon number =
9702_w21_qp_42
THEORY
2021
Paper 4, Variant 2
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Carbon-15 (15 6 C) is an isotope of carbon that undergoes radioactive decay to nitrogen-15 (15 7 N), which is a stable isotope of nitrogen. Radioactive decay is both a random and a spontaneous process. State what is meant by: random spontaneous. A small sample of carbon-15 decays. The mass M of carbon-15 in the sample decreases with time t. shows the variation with t of the value of ln (M / 10–16 g). – 8 – 7 – 6 – 5 – 4 In (M / 10–16 g) t / s State how demonstrates that radioactive decay is random. On , draw the straight line of best fit. Show that the decay constant λ of carbon-15 is given by the magnitude of the gradient of your line in . Use your line in to determine λ. Give a unit with your answer. λ = unit Use your answer in to calculate the half-life of carbon-15. half-life = s The equation for the decay of carbon-15 can be written as 6C 7N + 0 –1β + 0 0ν. State and explain how the mass of the products of the decay must compare with the mass of the carbon-15 nucleus.
9702_w22_qp_41
THEORY
2022
Paper 4, Variant 1
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Carbon-15 (15 6 C) is an isotope of carbon that undergoes radioactive decay to nitrogen-15 (15 7 N), which is a stable isotope of nitrogen. Radioactive decay is both a random and a spontaneous process. State what is meant by: random spontaneous. A small sample of carbon-15 decays. The mass M of carbon-15 in the sample decreases with time t. shows the variation with t of the value of ln (M / 10–16 g). – 8 – 7 – 6 – 5 – 4 In (M / 10–16 g) t / s State how demonstrates that radioactive decay is random. On , draw the straight line of best fit. Show that the decay constant λ of carbon-15 is given by the magnitude of the gradient of your line in . Use your line in to determine λ. Give a unit with your answer. λ = unit Use your answer in to calculate the half-life of carbon-15. half-life = s The equation for the decay of carbon-15 can be written as 6C 7N + 0 –1β + 0 0ν. State and explain how the mass of the products of the decay must compare with the mass of the carbon-15 nucleus.
9702_w22_qp_43
THEORY
2022
Paper 4, Variant 3
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Define radioactive decay constant. Show that the decay constant λ is related to the half-life t 1 2 of a radioactive isotope by the expression λ t 1 2 = ln2 A small volume of solution containing the radioactive isotope sodium-24 (2 1Na) has an initial activity of 3.8 × 104 Bq. Sodium-24, of half-life 15 hours, decays to form a stable daughter isotope. All of the solution is poured into a container of water. After 36 hours, a sample of water of volume 5.0 cm3, taken from the container, is found to have an activity of 1.2 Bq. Assuming that the solution of the radioactive isotope is distributed uniformly throughout the container of water, calculate the volume of water in the container. volume = cm3
9702_m18_qp_42
THEORY
2018
Paper 4, Variant 2
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Americium-241 is an artificially produced radioactive element that emits α-particles. A sample of americium-241 of mass 5.1 μg is found to have an activity of 5.9 × 105 Bq. Determine, for this sample of americium-241, the number of nuclei, number = the decay constant, decay constant = s–1 the half-life, in years. half-life = years Another radioactive element has a half-life of approximately 4 hours. Suggest why measurement of the mass and activity of a sample of this element is not appropriate for the determination of its half-life.
9702_s10_qp_42
THEORY
2010
Paper 4, Variant 2
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Americium-241 is an artificially produced radioactive element that emits α-particles. A sample of americium-241 of mass 5.1 μg is found to have an activity of 5.9 × 105 Bq. Determine, for this sample of americium-241, the number of nuclei, number = the decay constant, decay constant = s–1 the half-life, in years. half-life = years Another radioactive element has a half-life of approximately 4 hours. Suggest why measurement of the mass and activity of a sample of this element is not appropriate for the determination of its half-life.
9702_s10_qp_43
THEORY
2010
Paper 4, Variant 3
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The element strontium has at least 16 isotopes. One of these isotopes is strontium-89. This isotope has a half-life of 52 days. State what is meant by isotopes. Calculate the probability per second of decay of a nucleus of strontium-89. probability = s–1 A laboratory prepares a strontium-89 source. The activity of this source is measured 21 days after preparation of the source and is found to be 7.4 × 106 Bq. Determine, for the strontium-89 source at the time that it was prepared, the activity, activity = Bq the mass of strontium-89. mass = g
9702_s12_qp_42
THEORY
2012
Paper 4, Variant 2
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An isotope of an element is radioactive. Explain what is meant by radioactive decay. At time t, a sample of a radioactive isotope contains N nuclei. In a short time Δt, the number of nuclei that decay is ΔN. State expressions, in terms of the symbols t, Δt, N and ΔN for the number of undecayed nuclei at time (t + Δt), number = the mean activity of the sample during the time interval Δt, mean activity = the probability of decay of a nucleus during the time interval Δt, probability = the decay constant. decay constant = The variation with time t of the activity A of a sample of a radioactive isotope is shown in . A t ½ 2t ½ 3t ½ t The radioactive isotope decays to form a stable isotope S. At time t = 0, there are no nuclei of S in the sample. On the axes of , sketch a graph to show the variation with time t of the number n of nuclei of S in the sample. n t ½ 2t ½ 3t ½ t
9702_s15_qp_41
THEORY
2015
Paper 4, Variant 1
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Questions Discovered
119