Q7 · 2023 · Paper 1Simple familiar1 mark
QUESTION 7
An electron and positron can annihilate into a photon, producing another electron and positron pair in the process. An outcome of this interaction is that
(A)
total mass decreases.
(B)
fewer baryons will be produced.
(C)
the lepton number does not change.
(D)
the number of particles will decrease.
WORKED SOLUTION
1 markAnswer C
ANSWER
C
Worked solution
Electron–positron annihilation and pair production conserve total lepton number. The particle count can change, but the conserved quantum numbers do not. Option C.
Selects option C.
Worked explanation by QCE Vault; correct option verified against the QCAA answer key.