Physics (AS & A Level) · May / June 2016 · Paper 41 · Question 13
9702
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Copper-66 is a radioactive isotope. When a nucleus of copper-66 decays, the emissions include a β− particle and a γ-ray photon. The count rate produced from a sample of the isotope copper-66 is measured using a detector and counter, as illustrated in Fig. 13.1. to counter detector radioactive sample shielding Fig. 13.1
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13(a)[3]
e.g. background count (rate)/radiation multiple possible counts from each decay radiation emitted in all directions dead-time of counter (daughter) product unstable/also emits radiation self-absorption of radiation in sample or absorption in air/detector window three sensible suggestions, 1 each [3]
13(b)[2]
A = A0 exp(– ln 2 × t / T½) 1.21 × 102 = 3.62 × 104 exp(– ln2 × 42.0 / T½) or 1.21 × 102 = 3.62 × 104 exp(–λ × 42.0) T½ = 5.1 minutes (306 s) [2]
13(c)[1]
discrete energy levels (in nuclei) [1]
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