Paper 1 Nuclear Physics Answers

Q	Answer	Reason
1	A	Nucleons are protons and neutrons.
2	B	Atomic/proton number defines the element.
3	A	Alpha particle is ${}_2^4\mathrm{He}$ nucleus.
4	C	A neutron changes into a proton, so proton number increases by one.
5	A	Gamma changes energy state, not nucleon/proton count.
6	D	Activity is the number of decays per unit time, measured in Bq.
7	A	Individual decay is unpredictable.
8	B	Half-life is the time for the activity or number of undecayed nuclei to halve.
9	A	Standard relation.
10	C	Corrected source count rate equals measured count rate minus background count rate.
11	A	Definition.
12	B	Nuclear energy associated with mass defect is $E=\Delta m{c}^2$.
13	A	Total binding energy increases.
14	D	Light nuclei fuse towards products with higher binding energy per nucleon.
15	A	Positive nuclei repel.
16	C	Ionising radiation can remove electrons from atoms or molecules.
17	D	Alpha radiation has a short range in air and is stopped by paper.
18	B	Gamma radiation is high-frequency electromagnetic radiation.
19	A	Material itself is present.
20	D	The neutrino idea accounts for missing energy and momentum in beta decay at H2 level.