definitions and concepts

• alpha decay

  the process of an unstable nucleus emitting an alpha particle to become more stable
• annihilation

  the process of a particle and its antiparticle colliding and being converted into energy

  • the energy is released in two photons to conserve momentum
• antiparticle

  all particles have a corresponding antiparticle with the same mass but opposite charge and conservation numbers
• baryon number

  a quantum number that is conserved in all particle interactions

  • baryons have a baryon number of +1 and non-baryons have a baryon number of 0
• baryon

  a class of hadron, that is made up of three quarks

  • the proton is the only stable baryon
• beta-minus decay

  the process of a neutron inside a nucleus turning into a proton, and emitting a beta-minus particle (an electron) and an antineutrino
• beta-plus decay

  the process of a proton inside a nucleus turning into a neutron, and emitting a beta-plus particle (a positron) and a neutrino
• electron diffraction

  the spreading of electrons as they pass through a gap similar to the magnitude of their de broglie wavelength

  • evidence of the wave-like properties of particles
• electron-volt, eV

  the work done to accelerate an electron through a potential difference of 1V

  • 1eV is equal to the charge of an electron
  • E=QV
• energy levels

  defined and distinct energies at which electrons can exist in an atom

  • an electron cannot exist between energy levels
• excitation

  the process of an electron taking in exactly the right quantity of energy to move to a higher energy level
• gauge boson

  the exchange particles that transmit the four fundamental interactions between particles
• ground state

  the most stable energy level that an electron can exist in
• hadrons

  a class of subatomic particle that experiences the strong nuclear interaction
• ionisation

  the process of an atom losing an orbital electron and becoming charged
• isotopic data

  data from isotopes that can be used for a purpose, such as carbon dating
• kaon

  a type of meson that decays into pions
• lepton number

  a quantum number that is conserved in all particle interactions

  • both electron lepton numbers and muon lepton numbers must be conserved
• lepton

  a group of elementary subatomic particles, consisting of electrons, muons, and neutrinos
• meson

  a class of hadron that is made up of a quark and antiquark pair
• muon

  a type of lepton that decays into electrons
• neutrino

  a subatomic particle whose existence was hypothesised to maintain the conservation of energy in beta decay
• nucleon number, A

  the sum of the number of protons and neutrons in a given nucleus
• nucleon

  a proton or neutron
• pair production

  the process of a sufficiently high-energy photon converting into a particle and its corresponding antiparticle

  • to conserve momentum, this usually occurs near a nucleus
• photon

  a packet of energy
• pion

  a type of meson and the exchange particle for the strong nuclear force
• positron

  a positively charged particle that is the antiparticle of an electron
• proton number, Z

  the number of protons present in the nucleus of a given element
• stopping potential

  the minimum potential difference required to stop the highest kinetic energy electrons from leaving the metal plate in the photoelectric effect
• strange particles

  particles that are produced through the strong interaction but decay through the weak interaction
• strangeness

  a quantum number that is conserved in strong interactions but not in weak interaction

  • this reflects that strange particles are always produced in pairs
• strong nuclear force

  a force that acts between nucleons in a nucleus to keep it stable

  • it is attractive at distances up to 3fm and repulsive at separations less than 0.5fm
• threshold frequency

  the minimum frequency of photons required for photoelectron to be emitted from the surface of a metal plate through the photoelectric effect

  • it is equal to the metal's work function divided by planck's constant
• work function

  the minimum energy required to remove an electron from a metal's surface