Definitions

• Alpha Decay


  The process of an unstable nucleus emitting an alpha particle (two protons and two neutrons) 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 a 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. It is 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
• Isotope


  Same number of protons but different numbers of neutrons
• 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 interactions. 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 of up to 3fm and repulsive at separations less than 0.5fm
• Threshold Frequency


  The minimum frequency of photons required for photoelectrons 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