SUMMARY - PART 2

• Annihilation is...

- When a particle meets its corresponding antiparticle, the pair annihilate. This means that both particles are destroyed producing two photons of equal energy travelling in opposite directions to conserve momentum.

• What is the sum of the photons energy after annihilation equal to?

- It is equal to the total energy (kinetic and rest energy) of the particle and antiparticle pair before annihilation.

• Why do the photons move off in opposite directions?

- It move after the annihilation in order to conserve momentum in the system.

• The minimum energy of the photons produced after annihilation ?

- the minimum energy of each photon produced is equal to the rest energies of the particle or anti.

E(min) = E(0)

• What is pair production?

- A single photon of energy equal to total rest energy of a particle - antiparticle pair can produce the pair.

• How is energy conserved in pair production?

- The energy of a single photon must be the same as the combined energy of the particle and antiparticle. The pair's total energy is equal to the energy of a single photon. (This includes both kinetic and rest energy.)

• Formula conserved energy in pair production.

- E(photon) = E(particle) + E(antiparticle) + KE(particle) + KE(antiparticle)