Q101 · Practice questionSimple familiar1 mark
QUESTION 101
During beta-minus decay, a neutron changes into a proton and an electron is emitted: . Which particle must be so that electric charge and lepton number are both conserved?
(A)
electron neutrino,
(B)
electron antineutrino,
(C)
positron,
(D)
photon,
WORKED SOLUTION
1 markAnswer B
ANSWER
B
Worked solution
Answer: B — electron antineutrino, .
A neutron has electric charge and lepton number . After the decay, the proton and electron together have charge , so must be neutral. The electron contributes lepton number , so must contribute . An electron antineutrino is neutral and has lepton number .
Key insight: a candidate particle must satisfy both conservation tests at the same time.
selects B.
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabus