Antimatter

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  • Created by: maddie
  • Created on: 29-11-12 20:05
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  • Antimatter
    • when matter and antimatter particles meet, destroy each other -> radiation released.
      • used in PET scanner. p stands for positron (antiparticle of electron).
        • when used for brain scan, positron emitting isotope admistered to patient, some reaches brain via blood. Each positron emitted travels few cm then they annihilate each other producing two gammes rays
          • gamma rays picked up by detctors conected ot pc, image built up of where positron emitting nuclei are inside brain
    • Positron emission occurs when proton changes into neutron in unstable nuceli with too many protons
      • positron - antiparticle of electron = positive charge
      • uncharged particle, a neutrino also emitted
    • antimatter, predicted 1928 before 1st antiparticle, positrons discovery.
      • earlier - einstien shown mass of particle increases as it  travels faster and his equation E=mc^2 relates energy supplied to particle to increase in mass
        • also said rest mass (m0) of particle corresponds to rest energy (m0c^2) locked up as mass -showed m0c^2 must be included in conservation of energy
    • Dirac predicted existance of antiparticles/matter that unlock rest energy (m0c^2) whenver particle and antipartcle annihilate.
      • Dirac theory of antiparticles: each partcile antiparticle that ...
        • has exactly same rest mass as particle
        • has exactly oppsite charge to particle (if charged)
        • annihilates particle and itself if meet converting total mass -> photons
    • Dirac also predicted pair production - photon with sufficient energy could change to partcile - antiparticle pari whcih would then separate
  • Dirac theory of antiparticles: each partcile antiparticle that ...
    • has exactly same rest mass as particle
    • has exactly oppsite charge to particle (if charged)
    • annihilates particle and itself if meet converting total mass -> photons

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