Antiparticles and Photons

Question 1

What are antiparticles?

Answer 1

Have the same mass and rest energy but have a different charge

Question 2

What is pair production?

Answer 2

• Two protons are accelerated at high speeds
• When the two protons collide and extra proton and antiproton will be produced
• Other particles and antiparticles can be made from pair production

Question 3

Why do the particles produced in a detector curve away from each other?

Answer 3

Because they are in a magnetic field and have opposite charges

Question 4

What’s the minimum amount of energy needed for pair production?

Answer 4

The total rest energy of the particles that are produced

Question 5

What’s rest energy?

Answer 5

The energy produced if the mass of a particle was converted into energy

Question 6

What’s the equation for minimum energy for pair production?

Answer 6

E(min) = 2E₀

E(min) - minimum energy need in MeV
E₀ - rest energy of particle type produced in MeV

Question 7

What is annihilation?

Answer 7

• When a particle meets it’s antiparticle
• All the mass of the particle and the antiparticle is converted into energy in the form of two gamma rays

Question 8

What’s the equation for the minimum energy for annihilation?

Answer 8

E(min) = E₀

E(min) - minimum energy need in MeV
E₀ - rest energy of particle type annihilated in MeV

Question 9

What are the uses for annihilation in medicine?

Answer 9

• PET scanners
• A positron emitting isotope is injected into the blood stream
• The gamma rays produced from the annihilation between electrons and positrons are detected using a scintillator