Q193 · Practice questionComplex familiar7 marks
QUESTION 193 (7 marks)
Consider the Standard Model gauge bosons and the forces experienced by quarks and leptons. Gravity is outside this comparison.
a)[4 marks]
Identify the four gauge-boson types in the syllabus and give the interaction associated with each.
b)[3 marks]
Contrast the interactions experienced by a quark, an electron and an electron neutrino.
WORKED SOLUTION
7 marksPractice marking scheme
ANSWER
(a) Photon: electromagnetic; gluon: strong; W boson: weak; Z boson: weak. (b) Quark: strong, electromagnetic and weak. Electron: electromagnetic and weak. Electron neutrino: weak.
Worked solution
(a) Photons mediate the electromagnetic interaction. Gluons mediate the strong interaction. The charged and are the W type and mediate weak processes; the neutral Z also mediates the weak interaction. The Higgs is a boson but is not one of these four gauge-boson types.
(b) Quarks have colour and electric charge and participate in the strong, electromagnetic and weak interactions. Electrons have electric charge but no colour charge, so they participate in electromagnetic and weak interactions. Electron neutrinos have neither electric nor colour charge but participate in weak interactions.
Equivalent physically justified methods and consistent equivalent units accepted.
Displayed decimals are model answers; accept appropriate significant figures and consistent rounding from stated constants.
Part a: Identify photon and electromagnetic interaction.
Part a: Identify gluon and strong interaction.
Part a: Identify W and weak interaction.
Part a: Identify Z and weak interaction.
Part b: Give the three interactions for a quark with relevant charges.
Part b: Give electron interactions and absence of strong coupling.
Part b: Give neutrino weak interaction and absence of electric and colour charge.
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
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