Particle physics & Radiation

• what is meant by specific charge?

  the ratio of charge to mass
• what is the letter associated with a proton number?

  Z
• what is a nucleon?

  a constituent of the nucleus: a proton or a neutron.
• what letter represents nucleon number?


  A
• what is an isotope?

  a version of an element with the same number or protons but a different number of neutrons.
• 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 up to 0.5fm, attractive from 0.5-3fm, negligible 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 nucleons decay?

  alpha decay ( emission of a helium nucleus formed of 2 protons and 2 neutrons)
• 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 changes from udd to uud)
• how was the existence of the neutrino hypothesised?


  the energy of particles after beta decay was lower than before, a particle with 0 charge ( to conserve charge) and negligible mass must carry away this excess energy, this particle is the neutrino
• what is meant by beta minus decay?

  when a neutron turns into a proton, the atom releases an electron and an anti electron neutrino.
• what is an alpha particle?

  a particle contains two protons and two neutrons, the same as a helium nucleus.
• 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.
• what is the name of the antiparticle of an electron?

  positron
• 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.
• what is the minimum energy of a photon required to make a proton antiproton pair?


  2 x proton rest energy
• name the 4 fundamental forces?


  gravity, electromagnetic, weak nuclear, strong nuclear
• the virtual photon is the exchange particle of which force?


  the electromagnetic force
• 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
• what does the electromagnetic force act on?


  it acts on charged objects
• 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, stangeness
• what is a hadron?

  both baryons and mesons are hadrons, hadrons are made of 2 or more quarks held together by the strong nuclear force.
• what are the classes of hadrons?


  baryons - 3 quarks, mesons - 1 quark and 1 antiquark
• the pion and kaon are both examples of which class of particle?


  mesons
• the pion can be an exchange particle for which force?

  the strong nuclear force
• what particle does a kaon decay into?

  a kaon decays into a pion
• give some examples of baryons

  proton - uud, neutron - ddu
• what is significant about a proton?

  it is the only stable baryon, and all baryons will eventually decay into protons
• what are some examples of leptons?


  electron, muon, neutrino, and the antiparticles of them.
• what does a muon decay into?

  an electron and 2 types of neutrino
• what is the strangeness value of a strange quark?


  -1
• is strangeness always conserved in the weak interaction?

  no, it is only conserved in the strong interaction, in weak interactions it can change by 0 , -1, and 1
• are electromagnetic waves transverse or longitudinal?

  transverse
• what phenomenon can be used to show that light behaves as a particle?

  the photoelectric effect
• describe the photoelectric effect.

  when light above a particular frequency is shone on metal, electrons are released - these released electrons are called photoelectrons