Particles and Radiation

Particles and Radiation

1. The Strong Nuclear Force

   • Holds together nuclei so they don't disintegrate.
   • Overcomes electrostatic force of repulsion to keep Protons and Neutrons together

2. Electromagnetic Waves

   • In a vacuum all waves travel at the speed of light (C)
   • Radio, Micro, Infrared, Visible, Ultraviolet, X-Ray + Gamma Ray
   • Consists of an Electric wave and a magnetic wave - travel at 90* in phase.
   • EM Waves are emitted when a e- slows or changes direction (e- moves to a shell of lower E.)
   • EM Waves are released in bursts of Photons
   • E=hf

3. Antimatter

   • Matter + Antimatter = Radiation
   • Positron emission takes place when a Pro-> Neu in an unstable nucleus with too many protons
   • Antiparticles have the same rest mass as particles and opposite charge.
   • Particle + Antiparticle = Annihilation

4. Annihilation

   • Particle + Antiparticle = 2 Photons
     • 1 Photon would mean Momentum is not conserved
   • Min Energy of a Photon = hfmin -> 2 = 2hfmin = 2E0

5. Pair Production

   • Photon -> Particle + Antiparticle
   • Min Freq. (fmin) Min E of Photon needed = hfmin = 2E0

6. The Electromagnetic Force

   • Force between 2 Charged particles which exchange a Virtual Photon
     • Feynman Diagrams

7. The Weak Nuclear Force

   • Holds all the neutrons and protons together in a nucleus
   • Stops n to p in B- decay or a p to n in B+ decay.
   • Must be weaker than the strong Force
   • Exchange Particle = W Boson
     • 0 Rest Mass
     • Very short range (0.001 fm)
     • +1 Charge

8. Beta Decay

   • A W Boson meets a neutrino or Antineutrino changing them into a B-/B+
   • If no neutrino / Antin.
     • W- -> B- + Antineutrino
     • W+ -> B+ + Neutrino

9. Electron Capture

   • Proton in a proton-rich nucleus changing into a neutron.
     • Weak interaction with an outer shell electron from outside the nucleus
   • W+ = changes e- -> Neutrino
   • P + N collide at high speed