Physics · May / June 2023 · Paper 42 · Question 9
0625
As printed in the paper
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9(a)[3]
α – no. of neutrons 2
β – no. of protons 0 and charge –1.6 × 10–19
γ – no. of neutrons 0 and charge 0 and (very) thick concrete / thick lead
9(b)[1]
(the nucleus has) one less neutron and one more proton
9(c)[4]
95 (counts / min)
initial count rate due to source = 550 – 30 (counts / min) OR 520 seen
(75 min =) 3 half-lives OR (count rate =) 1 / 8 (of initial count rate)
final count rate due to source = (520 / 8 =) 65
9(d)[2]
any two from:
limit time of exposurestore sources in lead boxeskeep distance from sourcesavoid contact OR use tongs OR wear gloves
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