antiparticles

• Photons are packets of electromagnetic radiation
• Electromagnetic spectrum


  A continuous spectrum of all the possible frequencies of electromagnetic radiation
• Frequency and wavelength relationship

  f = c/l, where c = 3.00 × 10^8 ms–1
• Energy of a photon

  E = hf = hc/l
• Planck constant


  6.63 × 10–34 Js
• Types of electromagnetic radiation

  • Visible light
  • Radio waves
  • Micro-waves
  • Infra-red
  • Ultra-violet
  • X-rays
  • Gamma rays
• When energy is converted into mass


  You get equal amounts of matter and antimatter
• Every particle has an antiparticle
• Particle-antiparticle properties

  • Same mass and rest energy
  • Opposite charge
• Antiproton


  A negatively-charged particle with the same mass as the proton
• Antineutrino


  The antiparticle of the neutrino
• Particle/Antiparticle pairs

  • Proton
  • Antiproton
  • Neutron
  • Antineutron
  • Electron
  • Positron
  • Neutrino
  • Antineutrino
• Neutrinos and antineutrinos are incredibly tiny
• You can create matter and antimatter from energy
• Rest energy of a particle

  The 'energy equivalent' of the particle's mass, measured in MeV
• Einstein's Special Theory of Relativity


  Energy can turn into mass and mass can turn into energy
• Minimum energy for a photon to undergo pair production is the total rest energy of the particles produced
• Minimum energy for pair production


  Only gamma ray photons have enough energy
• When a particle meets its antiparticle

  The result is annihilation
• Annihilation


  All the mass of the particle and antiparticle gets converted back to energy
• Antiparticles can usually only exist for a fraction of a second before annihilation
• Minimum photon energy for annihilation

  Emin = hfmin = E0
• Both photons need to have a minimum energy for energy to be conserved in annihilation
• Electron-positron pairs


  Usually produced because they have a relatively low mass
• The particle tracks are curved because there’s usually a magnetic field present in particle physics experiments
• They curve in opposite directions because of the opposite charges on the electron and positron
• what is a photon?


  Photons are Packets of Electromagnetic Radiation, The energy of a photon depends on the frequency of the radiation, they travel at speed of light 3 x 10 ^8 in a vaccum
• pair production


  Fire two protons at each other at high speed and you’ll end up with a lot of energy at the point of impact. This energy might be converted into more particles. If an extra proton is formed then there will always be an antiproton to go with it. It’s called pair production.
• equation for wavelength


  wavelength = speed of light / frequency
• what does em wave consist of?


  electric field and magnetic field traveling together in phase and vibrating, they travel at right angles to each other
• when do charged particles emit em waves

  fast moving electron stops slows down or changes direction ,when electron in a shell moves to a lower energy shell
• equation for photon enregy


  E= hf
• what is anti particles produced of?

  atmospheric cosmic rays and pair production
• annihilation


  particle and antiparticle pair meet and all their mass is converted into pair of photons traveling in opposing directions to conserve momentum as well as energy,
• pair production


  photon converted into equal amounts of matter and antimatter.

  only occurs when photon has greater energy than the total rest energy of 2 particles.

  extra energy is converted into ke.

  electron or nucleus moves in opposing direction of 2 particles to conserve momentum
• The minimum energy for a photon to undergo pair production is the total rest energy of the particles produced. The particle and antiparticle each have a rest energy of E0 so Emin=2E0=hfmin
• An annihilation is between a particle-antiparticle pair, which both have a rest energy E0. Both photons need to have a minimum energy, Emin, which when added together equals at least 2E0 for energy to be conserved in this interaction. So 2Emin = 2E0 and so Emin= hfmin=E0