Particle Physics Flashcards
Nucleon
proton or neutron found in nucleus
Suggest what you should remember when calculating mass of an atom
Mass of electron is negligible
Isotopes
Atoms with the same number of protons and a different number of neutrons
Specific Charge
Charge per unit mass for a particle
Describe how the strong nuclear force between two nucleons varies with their separation and its role in the nucleus of an atom
- strong nuclear force has a short range
- repulsive below 0.5fm
- attractive up to 3fm
- overcomes electrostatic repulsion between proton and neutron
- holds protons and neutrons together in the nucleus
Explain why the specific charge of an electron is approximately 2000 times that of a hydrogen nucleus
- hydrogen nucleus consists of a proton
- proton and electron have the same magnitude of charge
- proton has a relative mass 1 and electron is 1/2000
- specific charge of proton is approx 2000 times electron due to higher charge density
Suggest how charge and specific charge are different for isotopes
- charge remains the same as neutrons have no charge
- specific charge is greater for the isotope with the smallest mass number
Nuclide Notation
- A = nucleon number
- Z = proton number
Describe alpha decay
- unstable nucleus emits an alpha particle (helium nucleus)
- decays into a new daughter nucleus
- mass number reduced by four and atomic number reduced by 2.
Suggests what happens to alpha particle from alpha decay
Shoots off and eventually acquires electrons to become a helium atom
Describe beta - decay
- neutron changes into proton in nucleus
- unstable nucleus emits a beta particle (fast moving electron)
- antineutrino released
- new daughter nucleus formed
- same mass number and atomic number plus one
Describe beta + decay
- proton changes into neutron in nucleus
- unstable nucleus emits a beta particle (fast moving positron)
- neutrino released
- new daughter nucleus formed
- same mass number and atomic number minus one
Describe gamma decay
- excited nucleus releases gamma radiation (surplus of energy)
- after alpha or beta decay
- same nuclide just less energetic
How did beta decay lead to discovery of neutrino
- realised energy was not conserved in beta decay
- existence of neutrino hypothesised to account for conservation of energy
Photon
Packet or quantum of electromagnetic waves
Antimatter
Sub-atomic particle having the same mass but opposite charge of a given particle
Annihilation
- sub-atomic particle and its antiparticle collide
- convert their total mass into photons
- two photons are released to conserve momentum
Rest Mass/Energy
- energy an object has when it is stationary
- E=mc^2
- hypothesised mass of an object increases with its velocity so rest mass is its minimum energy
Electron volt
- energy transferred when an electron is moved through a potential difference of one volt
- eV = magnitude of charge of electron
1. 6x10-19 J
Pair production
- photon with sufficient energy interacts with orbital electron (to conserve momentum)
- converts its energy into a particle-antiparticle pair which separates
Name gauge boson and particles affected by electromagnetic force
Virtual photon
Charged particles only
Name gauge boson and particles affected by weak interaction
W+ and W-
All affected
Name gauge boson and particles affected by strong force
Pion (Gluon)
Hadrons only
Name gauge boson and particles affected by gravity
Graviton
Any particles with mass