Particle Physics Flashcards
charge of proton/electron
1.6*10^-19C
ions and nuclei have charge but atoms don’t
mass of nucleon
1.67*10^-27kg
mass of electron
9.1*10^-31
Calculating Specific Charge
charge on particle/mass of particle
(INCLUDING MASS OF ELECTRONS)
(C/kg)
4 fundamental forces
Strong Force
Weak Force
Electromagnetic Force
Gravity
Strong Force
holds nucleons together
attracts: 0.5-3fm
repels:>0.5fm
exchange particle: gluons
Weak Force
responsible for decay to more stable particle
range: 10^-17m
Effects particles with mass(FEMIONS)
Exchange particlw: W+, W-, Z0
Electromagnetic force
responsible for most particle interactions
Needs charged particcals
range: infinite
exchange particle: photons
gravity
weakest force but is ACCUMILATIVE so greatest overall effect
Affects those with mass
range: infinite
Echange pasrticle: GRAVITONS
Alpha Decay
only has 2 or 3 DISCRETE energies
…easy to see momentum is conserved
X –> Y+alpha particle
Beta Decay
CONTINUOUS spectrum of energy but all beta particles should have same energy for conservation of momentum
… must be another particle, 2 particles going at different angles so different energy
X –>Y+beta particle+anti neutrino
conservation of lepton number
Electron Volt
coulombs*volts
1eV= 1.6*10^19
Total particle energy=
rest energy(mc^2)+Ke
Anhilation
particle and antiparticle colliding forming 2 photons
to conserve energy and momentum
Pair Production
energetic photon can suddenly transform into a particle and its antiparticle
detecting pair production
they leave distinct trachs and bend in magnetic field
(track from their ionization path)
in cloud chamber or bubble chamber
Everything about Planks Constant
h=6.6* 10^-34Js
E=hf
manipulate equation with c=f(lamda)
What are exchange particles
virtual particles, unobservable
larger molecules, shorter the range of force (because they can only exist for smaller amount of time)
Why have exchange particles
To conserve energy,momentum and charge
Hadrons
Baryons (3 quarks)
Mesons (2 quarks)
Quarks are fundemental
Neutrons unstable outside neucleus
Leptons
Electron, muon, neutrinos
All fundamental
Some charged some not
What to balance in particle interaction
Energy momentum
Charge
Baryon and lepton number
Excitation and Deexcitation
Electrons exist in discrete energy levels so need discrete energy photons to move to higher energy level (create absorption spectrum)
Electrons deexcite and release photon of specific frequency (emissions spectra)
Florescent tubes
1) voltage accelerates electrons
2) Mercury vapour excited, and deexcire to release UV rays
3) phosphorous coating excited by UV then deexcites releasing visible light
Why are florescent tubes at low pressure
Allows electrons to accelerate enough, less collisions with atoms so more likely to have enough energy
Electron diffraction
Forms concentric rings
Diffracrs around “slits” of atom spacing in crystals
De Broglie Wavelength
Wavelength=h/p
p=mv
