Unit 2: Particles and radiation

• 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.
• 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.
• 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.
• Meson: A class of hadron that is made up of a quark and antiquark pair.
• Muon: A type of lepton that decays into electrons.
• Baryon: A class of hadron, that is made up of three quarks. The proton is the only stable baryon.
• Nucleon: A proton or neutron.
• Nucleon Number (A): The sum of the number of protons and neutrons in a given nucleus.
• 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.
• 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.
• Photon: A packet of energy.
• Positron: A positively charged particle that is the antiparticle of an electron.
• 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.
• 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.
• 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.
• 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.
• Excitation: The process of an electron taking in exactly the right quantity of energy to move to a higher energy level.