What is a nucleon?
A constituent of the nucleus : a protons or a neutron
State a use of radioactive isotopes
Carbon dating - the proportion of carbon - 14 in a material can be used to estimate its age
What is the strong nuclear force?
The fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons
Describe the range of the strong force?
Repulsive ~ 0.5fm
Attractive ~0.5-3fm (greatest ~1fm)
Zero past 3fm
What makes a nucleus unstable?
Nuclei which have too many of either protons or neutrons or both
How do nuclei with too many neutrons decay?
Beta minus decay in which a neutron decays to a proton by the weak interaction (quark character has changed)
How was the existance of the neutrino hypothesised?
The energy of particles after beta decay was lower than before, a particle with 0 charge (to conserve change) and negligible mass must carry away this excess energy, this particle is the neutrino
What is meant by beta minus decay?
When a neutrn turns into a proton, the atom releases an electron and an anti-electron neutrino
What occurs when a particle and antiparticle meet?
Annihilation
The mass of the particle and antiparticle is converted back to energy in the form of 2 gamma ray photons which go in opposite directions to conserve momentum
What is pair production?
A gamma ray photon is converted into a particle-antiparticle pair.
Name the 4 fundamental forces.
Gravity
Electromagnetic
Weak nuclear
Strong nuclear
What type of particles are affected by the strong nuclear force?
Hadrons
What is the exchange particle of the weak nuclear force?
The W boson
When does weak nuclear interaction occur?
When quark character changes, it affects all types of particles.
Which properties must be conserved in particle interactions?
Energy
Charge
Baryon number
Lepton number
Momentum
Strangeness ONLY FOR STRONG INTERACTIONS
What is a hadron?
Baryons and mesons (made of two or more quarks held together by the strong nuclear force)
What are the classes of hadrons?
Baryons, mesons
The pion can be an exchange particle for which force?
the strong nuclear force
What are some example of leptons?
Electron
Muon
Neutrino
Tau
The antiparticles of the above
What does a muon decay into?
Is strangeness always conserved in weak interaction?
No, strangeness is ony conserved in the strong interaction it can change by +-1 or not in weak interaction
How are strange particles prodced and how do they decay?
Produced through strong interaction
Decay through the weak interaction
Lepton interaction types
All leptons participate in the weak interaction (by emitting or absorbing a W boson), including charged leptons decaying into lighter leptons
Only charged leptons participate in electromagnetic interaction by emitting or absorbing a virtual photon
No lepton participate in the strong interaction
Feynman diagram for repulsion of electrons
Electromagnetic interaction
Two electrons approach each other and they are repelled then they change direction as a virtual photon passes between them.
Feynman diagram for proton repulsion
Electro magnetic repulsion
Two protons approach each other and they are repelled, they then change direction as a virtual photon passes between them.
Beta minus and beta plus decay equations
Feynman diagram for proton and anti neutrino interaction
An antineutrino can interact with a proton and make it change into a proton. A beta minus particle (an electron) is created and emitted as a result of the change.
W+ from p to v
Feynman diagram for neutron and neutrino interaction
A neutrino can interact with a neutron and make it change into a proton. A beta minus particle (an electron) is created and emitted as a result of the change.
W- n to v
Feynman diagram for beta plus decay
Feynman diagram for beta minus decay
Feynman diagram for electron capture
Pair production
The creation of a subatomic particle and antiparticle from a photon with the sfficient rest energy
electron capture
A type of decay
electron proton collision
Beta plus decay feynman diagram
Beta minus decay feynman diagram
What are the main constituents of an atom?
Proton
Neutron
Electron
What is meant by specific charge?
The charge to mass ration, C/kg
What is an isotope?
A version of an element with the same number of protons but a different number of neutrons
Use of radioactive isotopes
Carbon dating - the proportion of carbon-14 in a material can be used to estimate its age
How do nuclei with too many nucleons decay?
Alpha decay - emit 2p and 2n
What is an alpha particle?
A particle contains two protons and neutrons
What is an antiparticle?
For each particle there is an antiparticle with the same rest energy and mass but all other properties are the opposite of its respective particle.
Does every particle have an antiparticle?
yes
Name of the antiparticle of an electron?
Positron
What is the antiparticle of pion 0
pion 0
What is the minimu energy of a photon required to make a proton-antiproton pair?
2 x proton rest energy
The vitual photon is the exchange article of which force?
The electromagetic force
What does the electromagnetic force act on?
It acts on charged objects, for example when a positively charged ball repels another positively charged ball
Examples of mesons
pion and kaon
What particle does a kaon decay into?
pion
Examples of baryons and its quark structure
proton -uud
neutron - ddu
What is significant about a proton?
It is the only stable baryon
All baryons will eventually decay into protons
What is the straangeness value of a strange quark?
-1
what are forces between particles caused by?
exchange particles
what is an antiparticle?
Antiparticles have the same rest energy and mass but all its other properties are opposite the particles
What can SNF compensate for?
But as it doesn't have a charge it can get close to the protons to then compensate for the repulsion of two protons.
Why do large nuclei have more neutrons?
as the protons repel each other and the more protons there are the greater the electrostatic force of repulsion and so the greater the strong force required to keep it stable but adding more protons will increase the electrostatic force of repulsion and so the number of neutrons become more than that of protonsLarger atoms need more neutrons to compensate more the electrostatic force
when is an atom stable?
if the forces among the particles that make the nucleus are balanced, an atom is unstable if these forces are unbalanced (the nucleus has an excess of internal energy)
total energy equation of a particle
Total energy = m0c^2 + KE
electron neutrino mass, rest energy, charge, generation,spin
~0,1,1/2
electron antineutrino mass, rest energy,charge
~0
range of gravitational force and what does it act on
infinite, holding matter in planets, stars and galaxies
unstable nuclei description, big nuclei vs small nuclei
are those which have too many protons or neutrons or both, causing the SNF to not be enough to keep them stable, and so the nuclei will decay in order to become stable.The strong nuclear force and the electrostatic force keep the nuclei of smaller atoms stable but can cause instability in larger atomsThe balance of protons and neutrons needs to be rightLarger atoms need more neutrons to compensate more the electrostatic forceHowever after a certain size no matter what the ratio of protons to neutrons, the nucleus will be too big to be stable
power equation (particles)
P = E/t & E = hfTherefore P=hf/t
why must the minimum frequency be met for pair production
Pair production cannot occur if the frequency is below a certain amount as E = hf so the energy of the photon is proportional to its frequency. When pair production occurs the energy is converted to mass according to the equation E = mc2. If the energy/frequency is below the conversion to the mass/rest energy of the particle and antiparticle pair the event will not occur.
annhilation diagram
pair production diagram
muon neutrino
Symbol,Relative charge,Relative mass,generation,spin
vp,0,~0,2,1/2
Strong force
Relative strength,EXCHANGE PARTICLE,RANGE (m),ACTS ON
1,Gluon(g),3 x 10^-15,Hadrons, holding electrons in atoms;holding atoms together
What is a guage boson?
A gauge boson is a force carrier, a bosonic particle that carries the forces
what do no leptons interact in
strong interaction
muon
Symbol,Relative charge,Relative mass,Rest mass(MeV).generation,spin
μ-,-1,-1,106,2,1/2
positron generation,charge,spin
1,1,1/2
electron repusion (EM repulsion) explaination and feynman diagram
Here two electrons approach each other and they are repelled then they change direction as a virtual photon passes between them (bottom half before interaction, top half after interaction
mesons composition
Comprised of a quark and an antiquarkMesons are their own particle e.g. K+and K- are anti particles of each other
beta plus and beta minus decay equations and feynman diagrams
p → n + e+ + Ve (+)
___
n → p + e − + Ve (-)
electron capture and electron proton collission equations and feynman diagrams
Electron capture: p + e- → n + νe Electron proton collision: p + e- → n + νesecond diagram iswrong it is the wron direction
graph of electrostatic force of repulsion vs distance
The electrostatic force extends far beyond the nucleus10fm is the diameter of the nucleus
why does a photon need to pass near an atom for pair production to occur
A single photon with sufficient energy and passing near another particle or atom can create a particle-antiparticle pair to conserve charge as photons are neutral (i.e. from energy -> mass)A photon has to be passing near an atom as, when a photon interacts with an orbital electron or a nucleon within the nucleus, the energy of the photon is used to create a particle-antiparticle pair. In order to conserve momentum, the photon needs to interact with interacting particle
electron antineutrino generation,charge,spin
1,0,1/2
Weak interaction
Relative strength,EXCHANGE PARTICLE,RANGE (m),ACTS ON
~10-5
,W boson (W+ or W-),10^-17 (due to high mass),All particles, beta decay, decay of unstable hadrons
diagram of the classification of particles
minimum energy of a photon for pair production
what do only charged leptons interact in
only charged leptons participate in the electromagnetic interaction by emitting or absorbing virtual photons (i.e. not neutrinos)
Charged leptons decay into lighter leptons by the weak interaction
beta plus decay
when a proton turns into a neutron and a positron and a neutrinoThis occurs if a nucleus is proton rich (if a nucleus is neutron rich it carries out beta minus decay)
Electromagnetic/Electrostatic
Relative strength,EXCHANGE PARTICLE,RANGE (m),ACTS ON
~10^-2Virtual ,photon (γ),Infinite (virtually no mass),Charged particles, holding electrons in atoms, holding atoms together
What is the weak nuclear force responsible for?
The weak nuclear force is responsible for beta decay, electron capture and electron-proton collision
when light is shone though certain elements what will occurr?
Only certain frequencies will be absorbed
what is annihilation
Annihilation is where a particle and its corresponding antiparticle collide, as a result their masses are converted into energy (radiation energy) and produce 2 photons in the process
what happens during annhilation and properties
This energy along with the kinetic energy of the two particles is released in the form of 2 photons moving in opposite directions in order to conserve momentumIt’s always two photons back to back, never just oneAt high energies, massive particles can be created not just photonsIn reality any particle-antiparticle can annihilate not just opposite ones.
spins of bosons vs leptons
Particles that have integer spins are known as BosonsParticles that have half integer spins are known as leptons
mesons quark grid
proton repulsion explaination and feynman diagram
Two protons approach each other and they are repelled, they then change direction as a virtual photon passes between them.
What happens to the W+ boson in interactions
The W boson in each beta decay meets a neutrino or antineutrino, changing them into a Beta minus particle (electron) ora beta plus particle (positron)The W- boson decays into a Beta- particles and an antineutrinoThe W+ boson decays into a Beta+ particle and a neutrino
Feynman diagram rules
Incoming particles start at the bottom,and travel upwards (the higher you go, the further in time)Baryons (heavy hadrons) and leptons (light particles) stay on their own sidesCharges on both sides must be balancedExchange particles (gauge bosons) are represented by wiggly linesAll other particles are represented by straight lines
electron capture vs electron proton collission
The equations for electron capture and an electron-proton collision are the same however a different exchange particles used, not electrostatic interaction but a weak force interaction
neutrino and anti neutrino interactions explainations and feynman diagrams
quarks properties, spin and charge
fundamental propertiesAll have spin of ½ fermions3 generations with increasing massCharge is ⅔ foruptype and -⅓ for down type
muon properties
Unstable : 2.2 micro second half life
fundamentalA heavy electron : same charge as the electron207 times heavier at 106 MeV
anti muon and muon decay equation
top line anti muon and bottom muon
what do all quarks participate in
All quarks participate in strong interactionBy emitting or absorbing a virtual gluonAll quarks participate in em interactionsBy emitting or absorbing a virtual photon, because they are all chargedAll quarks participate in weak interactionBy emitting or absorbing a virtual W+ or W-They always change their typeThey may change their generation
Potassium emits electrons from its surface when blue light is incident on it. Extremely intense red light produces no electrons.
Explain these observations in terms of photons and their energy
Energy of a light photon exceeds the work function
Red light does not exceed this as it has a higher wavelength due to f = c/wavelength
One photon interacts with one electron to cause photoemission
Photon energies are independent of intensity
Feynman diagram strong interaction
Describe how a beam of fast moving electrons is produced in the cathode ray tube of an oscilloscope
Thermionic emission
Heating the cathode
An electric field between the anode and cathode is created
What is likely to happen to a positron shortly after it is created
Annihilate with an electron to create two photons moving in opposite directions
Properties of strange particles
Created in pairs
Normally decays into combinations of pion, proton and neutron
Contains one strange quark
Decays via weak interaction
Half-life is relatively long compared with half life of typical particle decaying via strong interaction
What does the penetration of a photon dependant on
Energy