Particles + Quantum Flashcards
Nucleon definition
Proton or neutron inside a nucleus
Isotope definition
Same number of protons but with different number of neutrons in nucleus
Strong nuclear force definition
Force in the nucleus that overcomes the strong electrostatic repulsion of protons and neutrons, keeping them together
Attraction up to 5fm, repulsion below 1fm
Only affects hadrons
Mediated by gluons/pions
Specific charge equation
Charge/mass
Add up charges and the masses
Beta radiation (B-)
- Where does it happen
- What is emitted
Beta radiation consists of fast-moving electrons
Occurs in an unstable nucleus when a neutron turns into a proton
Beta particle created immediately and is emitted
ANTINEUTRINO with no charge also emitted.
Positron emission (B+)
- Why does it happen
- What is emitted
Takes place when a proton changes into a neutron in an unstable nucleus with too many protons.
Antiparticle of electron, carries +ve charge
NEUTRINO is emitted
Electron capture
When a proton turns into a neutron due to the interaction with an electron (WEAK INTERACTION)
Annihilation
When a particle and its antiparticle meet, they destroy each other and become radiation.
Total energy of the particle/antiparticle pair before the collision is taken away by 2 photons
Energy before = energy after
2(Rest energy) = 2hf
Minimum energy of each photon produced = rest energy of the particle/antiparticle
GAMMA RANGE OF EM SPECTRUM (large energy)
Momentum is conserved when 2 photons are emitted
Binding energy definition
Work done to separate a nucleus into its constituent neutrons and protons
Binding energy equation(s)
Binding energy = mass defect * c^2
Binding energy in MeV = mass defect in u * 931.3
Pair production
When one gamma PHOTON turns into a particle and antiparticle
Energy of photon = total energy of particle-antiparticle pair
E(photon) = 2E0 + 2(KE)
Mass defect definition
The difference in mass between the separated nucleons and the nucleus
Different particle groups
Leptons
Hadrons (quarks), including
- Baryons
- Mesons
Differences between leptons and hadrons
Leptons do NOT interact through the strong interaction
Hadrons interact through the four fundamental interactions
Hadrons: lepton number = 0
Differences between baryons and mesons
Baryons decay into protons (directly/indirectly)
Baryons have B=1, mesons have B=0
Baryons: qqq
Mesons: qq’ ( ‘ = anti)
Conservation rules
Conservation of charge:
Charge before = charge after
Conservation of energy:
Total energy of particles + antiparticles before the collision = rest energy + kinetic energy
Total energy of particles + antiparticles after the collision = rest energy + kinetic energy
Rest energy of products = total energy before - kinetic energy of products
Conservation of lepton numbers:
Total lepton number for any branch = total lepton number for that branch after the change
Baryon number before = baryon number after
Quark combinations of:
pi+
pi-
pi
ud’
u’d
uu’ and dd’
Exchange particles for interactions
Electromagnetic:
Photon. Range is infinite. Acts on CHARGED PARTICLES
Strong:
Gluons for INDIVIDUAL quarks, mesons for hadrons.
Range: 10^-15m. Acts on QUARKS
Weak:
w+, w-, zº (basons). range: 10^-18m. Act on QUARKS AND LEPTONS
Gravitational: graviton (undiscovered)
Describe how the variation of the strong nuclear force with distance contributes to the
stability of the deuterium nucleus. (3 marks)
Short-range attraction to 3fm
Shorter-range repulsion to 0.5fm
Prevents protons and neutrons from moving closer and further apart
Antiparticle definition
Particle with equal rest mass/energy
But opposite charge/baryon and lepton number
Explain in terms of energy changes how line emission spectra are produced (3)
Energy levels are discrete –> emitted photon energy is discrete
Photon produced by electrons moving to lower energy levels
E = hf
Different wavelengths/frequencies are produced.
What is the photoelectric effect?
The emission of photons from a metal surface
When the surface is illuminated by light of frequency greater than the threshold frequency
Photoelectric effect observations
Below a certain frequency (threshold frequency) no (photo)electrons are ejected
Electrons are ejected immediately when illuminated with UV light
Intensity of EM radiation is increased, more photoelectrons are ejected
When the frequency increases, the kinetic energy of the photoelectrons increases
Intensity and frequency - how do they adjust the result of the photoelectric effect?
Intensity affects number of photoelectrons emitted
Frequency of light affects the kinetic energy of the photoelectrons
Excitation definition
Process when an atom absorbs energy without becoming ionised
As a result of an electron inside an atom moving from an inner shell to an outer shell
Explain the difference between excitation and ionisation
In both cases, an electron receives energy
Excitation promotes an (orbital) electron to a higher energy level, allowing it to go to an outer shell (DOESN’T LEAVE ATOM)
Ionisation occurs when electron receives enough energy to LEAVE the electron
Why is the electron configuration in an excited atom unstable?
Because an electron that moves to an outer shell leaves a vacancy
When this space is eventually filled, the electron emits a photon
The atom moves to a lower energy level
Linking rest mass to rest energy
(Rest) Energy = (rest) mass * c^2
Joules to (M)eV
Joules/1.6e-19 = eV
Joules/1.6e-13 = MeV
Quark combinations of: k0 k'0 k+ k-
ds’
d’s
us’
u’s
Ionisation energy definition
The minimum amount of energy needed to remove an electron from the ground state
