Lesson 8.4.1

8.4.1 Quark-lepton model and antiparticles Quiz: Pearson Edexcel Physics, Unit 8

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 8.4.1, Quark-lepton model and antiparticles: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 8: Nuclear and Particle Physics, written with Revision Ninja.

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The 20 questions

  1. What are baryons made from in the standard quark-lepton model?

    • Two quarks and one lepton
    • One quark and one antiquark
    • Three leptons bound together
    • Three quarks

  2. What are mesons made from in the standard quark-lepton model?

    • Three quarks
    • Two leptons and one quark
    • One quark and one antiquark
    • One lepton and one photon

  3. Which of the following particles is a fundamental lepton?

    • The neutron
    • The pion
    • The proton
    • The electron

  4. Which combination of quarks makes up a neutron?

    • Three up quarks
    • One up quark and two down quarks
    • One up quark and two anti-down quarks
    • Two up quarks and one down quark

  5. The quark-lepton model predicted the existence of a sixth quark. Which quark was this?

    • The bottom quark
    • The top quark
    • The charm quark
    • The strange quark

  6. What is the relationship between a particle and its antiparticle?

    • They have the same mass and opposite electric charge
    • They have the same mass and the same electric charge
    • They have opposite mass and the same electric charge
    • They differ in mass but have the same electric charge

  7. A proton is made of two up quarks and one down quark. What is its electric charge?

    • -1
    • 0
    • +2/3
    • +1

  8. A neutron is made from one up quark and two down quarks. What is its total electric charge?

    • Zero
    • +1
    • +2/3
    • -1

  9. A positive pion is made from an up quark and an anti-down quark. What is its electric charge?

    • -1
    • 0
    • +1
    • +2/3

  10. An antiproton is made from which quarks?

    • Two anti-up quarks and one anti-down quark
    • Two anti-down quarks and one anti-up quark
    • Two up quarks and one down quark
    • One anti-up quark and two strange quarks

  11. Which of these particles has baryon number +1?

    • The electron
    • The proton
    • The positron
    • The pion

  12. Which property is shared by a particle and its antiparticle?

    • The sign of electric charge
    • Mass and spin
    • Electric charge
    • The sign of lepton number

  13. What is the antiparticle of the electron?

    • The positron, with the same mass as the electron and charge +1
    • The antiproton, with charge -1 and a much larger mass
    • The neutrino, with zero charge and a mass that is negligible
    • The neutron, with zero charge and a larger mass

  14. In the neutron decay n -> p + e^- + antineutrino, which quark changes type?

    • No quark changes, because the decay involves only leptons
    • A strange quark changes into a charm quark
    • A down quark changes into an up quark
    • An up quark changes into a down quark

  15. What is the baryon number of a meson?

    • Zero
    • Two
    • One
    • Three

  16. Which conservation law prevents an electron from decaying into a single pion?

    • Lepton number conservation, because the electron has lepton number +1 but the pion has zero
    • Baryon number conservation, because the pion contains quarks and the electron does not
    • Charge conservation, because the electron and pion have different signs of charge
    • Momentum conservation, because a single pion cannot carry any momentum

  17. In the decay pi^+ -> mu^+ + neutrino (muon), why is lepton number conserved?

    • The antimuon has lepton number -1 and the muon neutrino has +1, summing to zero, which matches the pion's zero
    • Neither product carries lepton number, so the total is zero without any cancellation
    • The pion has lepton number -1, which exactly cancels the lepton number of the antimuon
    • The antimuon has lepton number +1 and the neutrino has zero, which sums to one

  18. A student claims the top quark was discovered before the quark-lepton model predicted it. Which response is correct?

    • The student is right: the top quark was observed in experiments before the model was written down
    • The student is right, because the model was written only after all six quarks were discovered
    • The student is wrong: the symmetry of the quark-lepton model predicted the top quark before it was observed
    • The student is wrong because the top quark is a lepton and so could not be predicted by the model

  19. What is the electric charge of a down quark, in units of the elementary charge e?

    • +1/3
    • -1/3
    • +2/3
    • -2/3

  20. Which particle is the antiparticle of the proton?

    • The antiproton, with charge -1
    • The neutron, with zero charge
    • The positron, with charge +1
    • The pion, with charge +1

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