AQA PHYS Paper 1

• Particle groups


  • Hadrons
  • Leptons
• Leptons


  Fundamental particles including electron, muon (heavy electron), and neutrino
• Lepton number


  Leptons have a lepton number of 1, their antiparticles have a lepton number of -1
• Types of neutrinos


  • Electron neutrinos
  • Muon neutrinos
• Quark flavours


  • Up
  • Down
  • Strange
• Strangeness


  Strange quarks have strangeness -1, antistrange quarks have strangeness +1
• Baryon number


  Baryons have a baryon number of +1 or -1 if they contain antiquarks
• Neutrons are up-down-down, protons are up-up-down
• Electromagnetic force


  Affects any charged particle, exchange particle is the photon
• Weak force


  Affects any particle, exchange particles are W+, W-, Z0 bosons
• Strong force


  Affects only hadrons, exchange particle is the gluon
• Electrostatic repulsion and strong force balance to stabilise nuclei
• Strong force range


  1. 4 fm, switches from attractive to repulsive at 0.5 fm
• In any interaction, charge, baryon number and lepton number must be conserved
• Feynman diagrams


  Represent weak interactions involving W+/W- bosons
• In beta minus decay, a down quark in the neutron decays to an up quark, turning the neutron into a proton
• Strangeness rules


  • Interactions involving leptons must be weak
  • Interactions involving only hadrons and conserving strangeness must be strong
  • Interactions not conserving strangeness must be weak
• Charge to mass ratio

  Charge in coulombs divided by mass in kilograms
• Types of radiation


  • Electromagnetic (emitted by electrons)
  • Gamma (emitted by nucleus)
  • Alpha (emitted in radioactive decay)
  • Beta (emitted in radioactive decay)
• Heavier nuclei are generally more unstable and likely to decay
• Alpha decay


  1. Nucleus emits a helium nucleus (2 protons, 2 neutrons)

  2. Daughter nucleus has 2 fewer protons
• Beta decay


  1. Neutron in nucleus turns into proton, electron and antineutrino are emitted

  2. Daughter nucleus has 1 more proton
• Electron-positron annihilation produces 2 photons to conserve momentum
• Rest energy/mass energy


  Energy = mc^2, can be converted to photon energy hf
• Pair production


  High energy photon converts into electron-positron pair
• Atomic energy levels


  Electrons orbit nucleus at discrete energy levels, can be excited to higher levels
• Electron de-excitation


  Electron falls back to lower energy level, emitting photon
• Ionization


  Electron can be excited to ionization level, leaving atom as free electron
• Energy level units


  Can be expressed in joules or electron volts (1 eV = 1.6x10^-19 J)
• Emission spectrum


  Shows wavelengths of photons emitted by an object, can identify its composition
• Absorption spectrum


  Shows wavelengths absorbed by a gas or plasma, also identifies composition
• Fluorescent tube


  Electrons accelerated through mercury gas, emit UV which excites phosphor coating, emitting visible light
• Wave-particle duality


  Photons exhibit both wave and particle properties
• Photoelectric effect


  Light shone on metal ejects electrons, kinetic energy depends on frequency not intensity
• Work function


  Minimum energy required to liberate an electron from a metal surface
• Electron diffraction


  Electrons exhibit wave-like diffraction patterns when fired at a target
• de Broglie wavelength


  Wavelength of a particle = h/p, where h is Planck's constant and p is momentum
• Electricity


  Flow of electric charge, transfers energy from source to components
• Lambda


  Wavelength of a particle
• Faster speed of a particle


  Smaller wavelength