Conservation laws, mass-energy and antimatterEdexcel International A Level Physics: Mind map

Exam questions on Conservation laws, mass-energy and antimatter

1. An electron and a positron, both moving very slowly, annihilate to produce two gamma-ray photons. The rest mass of an electron or of a positron is 0.511 MeV/c².
   Describe what happens to the mass of the electron and the positron in the annihilation and how energy is conserved.2 marks
2. A gamma-ray photon of energy 2.50 MeV passes close to a nucleus in a bubble chamber and produces an electron-positron pair. The chamber is in a uniform magnetic field. The recoil of the nucleus may be ignored.
   Calculate the total kinetic energy of the electron and positron.2 marks
3. Particle physicists quote the masses of particles in MeV/c² or GeV/c². A muon has a mass of 105.7 MeV/c². A proton and an antiproton each have a mass of 0.938 GeV/c². Use 1 eV = 1.60 × 10⁻¹⁹ J and c = 3.00 × 10⁸ m s⁻¹.
   Calculate the mass of the muon in kg.3 marks