Antiparticles and Photons

Antiparticles and Photons

1. Electromagnetic radiation

   • The electromagnetic spectrum- a continuous spectrum of the different frequencies of electromagnetic radiation
   • Frequency- the number of waves passing a certain point in a second
   • Wavelength of a wave- the distance between two adjacent crests of a wave
   • Higher frequency of electromagnetic radiation the greater its energy
   • Diagram

2. Photons

   • Einstein- EM waves only exist in discrete packets (photons)
   • E= hf
     • E- energy of photon (J)
     • h- Planck's constant
       • 6.63x10^-34
     • f- frequency (Hz)
   • f= c l
     • f- frequency (Hz)
     • c- speed of light
       • 3.0x10^8
     • l- wavelength (m)
   • Substituting the equations
     • E= hf= hc/ l

3. Antiparticles

   • Each particle has a corresponding antiparticle. They have the same mass and rest energy but opposite charges

4. Pair Production

   • When energy is converted into mass there is equal amounts of matter and antimatter
   • Only occurs if there is enough energy to energy to produce its masses
   • Must always produce a particle and it’s corresponding antiparticle
   • E.g. firing two particles at each other at high speed, at impact some of their energy can be converted into mass
   • E.g. if a photon has enough energy it can produce an electron positron pair, occurs when a photon passes too close to a nucleus

5. Pair production

   • The minimum energy needed is the total rest energy of the particles produced
   • Rest energy is the amount of energy that would be produced if all its mass was transferred into energy
   • Particle- antiparticle pair the rest energy is 2Eo
   • Emin = 2Eo
     • Emin- minimum energy needed in MeV
     • 2Eo- rest energy of particle type produced in MeV

6. Annihilation

   • When a particle and antiparticle meet they annihilate each other
   • All mass is converted back into energy to form two gamma photons
   • 2Emin = 2Eo
   • MeV to J
     • X10^6
   • MeV to eV
     • 1.60x10^-19