Exchange Particles and Reading a Feynman Diagram · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The messengers between particles

Science · Matter & Materials · ages 17-18
Name ______________________   Date ____________

  1. Which particle carries the strong force?

    • The W boson
    • The photon
    • The gluon

  2. Which particle carries the electromagnetic force?

    • The photon
    • The gluon
    • The W boson

  3. Which particles carry the weak force?

    • The gluon
    • The photon
    • The W and Z bosons

  4. In beta-minus decay, what does the emitted W boson become?

    • A proton plus a neutron
    • An electron plus an antineutrino
    • Two photons

  5. Which three quantities must balance at every vertex?

    • Charge, baryon number and lepton number
    • Charge, colour and spin
    • Mass, speed and temperature

  6. In a Feynman diagram, what does an arrow pointing backward in time mean?

    • A faster particle
    • An antiparticle
    • A heavier particle

  7. A proposed diagram breaks lepton number at one vertex but balances charge. What follows?

    • It is fine if charge balances
    • It needs a graviton
    • It is forbidden

  8. Electron capture pulls an atomic electron into a proton. What comes out?

    • A proton plus an electron
    • A neutron plus a neutrino
    • Two neutrons
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Answer key

For grown-ups. Fold this page away before handing over the rest.

The messengers between particles W1-mt_7Ka5cVpTVL-s1

  1. The gluon · Gluons bind quarks, while photons and W bosons serve other forces.
  2. The photon · The photon is the electromagnetic messenger and has unlimited range.
  3. The W and Z bosons · The heavy W and Z bosons carry the weak force over tiny ranges.
  4. An electron plus an antineutrino · The W leaves the quark vertex and materialises as an electron and antineutrino.
  5. Charge, baryon number and lepton number · Every total going in must equal the total coming out.
  6. An antiparticle · Backward in time reads as an antiparticle moving forward, with flipped charges.
  7. It is forbidden · All three books must balance, so one failure kills the diagram.
  8. A neutron plus a neutrino · The W exchange turns the pair into a neutron plus a neutrino.
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