Alvl P1: Particles (ch1/2) Cheat Sheet

specific charge:
charge to mass ratio

for an atom, is the charge (typically proton number unless an ion then the charge eg 2+ only) over the overall mass (proton and neutron number)

unstable nuclei decay to become more stable emitting radiation.

these can ionise other atoms/­mol­ecules which can be dangerous

Alpha decay (larger nuclei):
4 on the top, 2 on the bottom

Beta decay (smaller nuclei):
+ - p>n
- - n>p

*make sure lepton numbers are balenced
eg. beta- decay has anti electron neutrino



gamma radiation:*
is a high energy EM wave that can be emitted but this isnt due to decay but due to nucleus being in an metastable state (excess energy)

in a decay equation you would write the product number at the top with a small m
in a separate equation you take the element with the m and write it out with the product being without the m and the gamma ray

charge, energy and momentum, baryon­/lepton number must all be conserved in any intera­ction.
strang­eness doesnt need to be conserved, only in strong intera­ction

rules:
- particle decay > strang­eness is not always conserved
- pair production > strang­eness is always conserved



strang­eness:
- strange particles are produced by strong intera­ction
- to conserve strang­eness they are always created in pairs
eg. p + p = us^-s
- they decay via weak intera­ction but don't need to be created in pairs (don't have to be conserved)


proving conser­vation: (Relating to particle intera­ctions)

B^+/- --> occurs in a neutron (decay) - B⁺ = p>n
electron scatter --> come close and repel due to charge
P-N bond --> occurs in nuecleus due to strong force (also em however em is weaker than strong)
electron capture --> electron captured by a proton, therefore exchange particle is always from the proton (W⁺)
E-P collision --> electron collides with proton so exchange particle comes from the electron (w^-)

these are possible due to the fact that mass can be converted ubti energy and vice versa

Annihi­lation:
particle and antipa­rticle collide- mass is converted to two photons

minimum energy­/fr­equ­ency:
2mc² = 2hf

if the particles have kinetic energy this is added to the photons energy


Pair produc­tion:
a photon of sufficient energy is converted into a particle and its antipa­rticle

minimum freq photon for this:
hf = 2mc²

if photon has more than minimum needed, it is converted into Ek