8.4.2 Conservation laws and particle equations Quiz: Pearson Edexcel Physics, Unit 8

The 20 questions

1. Which three quantities must be balanced on each side of a particle equation?

   • Electric charge, mass number and atomic number
   • Number of photons, number of quarks and speed
   • Kinetic energy, electric charge and spin only
   • Electric charge, baryon number and lepton number

2. What is the baryon number of an antiproton?

   • +2
   • +1
   • 0
   • -1

3. What is the lepton number of an electron antineutrino?

   • 0
   • -1
   • +1
   • +2

4. Which equation is consistent with conservation of electric charge?

   • pi+ -> mu+ + mu-
   • pi+ -> mu- + nu_mu
   • pi+ -> mu+ + nu_mu
   • pi+ -> mu+ + mu+ + nu_mu

5. In the decay mu^- -> e^- + anti-nu_e + nu_mu, what is the total lepton number of the products?

   • +1
   • +2
   • -1
   • 0

6. A neutron decays by n -> p + e^- + anti-nu_e. What is the total lepton number of the products?

   • -1
   • 0
   • +2
   • +1

7. The reaction p + p -> p + n + pi^+ occurs. What is the total electric charge after the reaction?

   • 0
   • +3
   • +2
   • +1

8. In the decay pi^- -> mu^- + X, which particle is X?

   • The antimuon neutrino
   • The electron antineutrino
   • A photon
   • The muon neutrino

9. In the reaction e^- + p -> n + X, what is particle X?

   • The electron antineutrino
   • A positron
   • A photon
   • The electron neutrino

10. A proton and a neutron collide, and the products are a proton and a particle X, with charge conserved. What is the charge of X?

    • +1
    • +2
    • Zero
    • -1

11. A proton and a neutron are at rest, and a neutral particle X is produced with the other products. Which particle matches the requirement of zero charge?

    • A positive pion
    • A negative pion
    • A positron
    • A neutral pion

12. A neutron at rest decays into a proton and a negative pion. Which conservation law is violated?

    • Energy, because the products have greater total rest energy than the neutron
    • Charge, because the products have a net charge of -1
    • Baryon number, because the pion has baryon number -1
    • Lepton number, because a pion carries lepton number +1

13. Which equation is NOT consistent with conservation of electric charge?

    • n -> p + e^- + anti-nu_e
    • pi+ -> mu+ + nu_mu
    • pi+ -> mu- + nu_mu
    • pi^- -> mu^- + anti-nu_mu

14. A mu-plus decays into an e-plus, an electron neutrino and an antimuon neutrino. What is the total lepton number of the products?

    • +1
    • -2
    • 0
    • -1

15. In beta-plus decay, p -> n + e^+ + nu_e. What is the total lepton number of the products?

    • -1
    • +2
    • +1
    • 0

16. In neutron beta-minus decay, which particle must accompany the electron to conserve lepton number?

    • The electron neutrino
    • The electron antineutrino
    • A positron
    • A photon

17. Which particle equation is balanced for both charge and lepton number?

    • nu_mu + n -> p + mu^-
    • nu_mu + n -> p + mu^+
    • nu_mu + n -> n + mu^-
    • anti-nu_mu + n -> p + mu^-

18. Which particle has baryon number -1 and electric charge -1?

    • The positron
    • The antiproton
    • The electron antineutrino
    • The antineutron

19. A student claims an equation is balanced if the charges and baryon number balance, even if lepton number does not. Which response is correct?

    • The student is right, but only for decays that produce photons in the final state
    • The student is wrong because particle equations never need to balance any quantities
    • The student is wrong: lepton number must also balance, so all three quantities must be conserved in a valid equation
    • The student is right: lepton number does not need to balance in any particle equation

20. Which particle equation is forbidden by conservation of lepton number?

    • pi+ -> e+ + nu_e
    • pi- -> e- + anti-nu_e
    • pi+ -> e+ + anti-nu_e
    • pi0 -> gamma + gamma

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