Physics · May / June 2021 · Paper 42 · Question 11
0625
As printed in the paper
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11(a)(i)[3]
(initial CR adjusted for background = 220 – 20 =) 200
(after 1 half-life CR adjusted for background =) 100 OR
(detected CR) = 120
2.4 min
11(a)(ii)[2]
12 or 13
(12 + 20 =) 32 OR (13 + 20 =) 33
11(b)[3]
incorrect
container / (2 mm) plastic does not absorb / stop / block / is penetrated by γ
good extra detail e.g. any one of:
container / (2 mm) plastic absorbs / stops αpartially correct as statementneed lead to stop γγ is dangerous / harmful owtte
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