1.3 Particles - Photons and Antiparticles Flashcards
Photons:
Light could be released in particle-like packets of energy / EM waves, called photons
Planck’s constant:
h = 6.63 x 10^-34 J
Equation for photon energy:
E=hf or E=hc/wavelength
Electronvolt definition:
The work done in a moving electron across a potential difference of 1 volt
eV to J:
x 1.60 x10^-19
J to eV:
/ 1.60 x10^-19
Antimatter:
A particle of equal mass to a particle but of the opposite charge; antiparticle of electron called positron
Annihilation:
When a particle meets its own antiparticle, they annihilate each other
This is the process by which the mass of two particles is completely transferred to EM radiation to form 2 equal-energy photons moving in opposite directions
Equation for energy of annihilation:
E = mc^2
Momentum in annihilation:
Two photons conserve momentum
The total momentum of the electron-positron system is 0 therefore two photons with equal and opposite momenta must he produced to keep system momentum at 0
Rest mass:
= mass of body at rest
Rest energy:
= energy of body at rest (MeV)
Annihilation equation:
E(min) = hf(min) = E
Pair production:
When a sufficiently energetic photon passes close to a nucleus, the EM energy of the photon will be converted into particle-antiparticle pair
Pair production equation:
E(min) = hf(min) = 2E
Why does pair production have to have minimum energy equal to rest masses?
Minimum energy must be equal to the rest mass of the air produced as otherwise surplus energy would appear as kinetic energy carried by the particle and antiparticle
