Particles and Radiation

• what is the charge and mass of a proton?


  +1.6x10^-19 and 1.67x10^-27
• what is the charge and mass of a neutron?


  0 and 1.67x10^-27
• what is the charge and mass of an electron?


  -1.6x10^-19 and 9.11x10^-31
• what is specific charge and how do you calculate it?

  it is the ratio of an atoms charge to its mass specific charge = charge/mass
• What is an isotope?


  Atoms of the same element that have different numbers of neutrons
• what does electromagnetic force do in the nucleus?


  causes the positively charged protons in the nucleus to repel each other
• what does gravitational force do in the nucleus?


  causes all the nucleons in the nucleus to attract each other due to their mass
• what force stops the electromagnetic force tearing the nucleus apart?

  strong nuclear force
• what is the range of strong nuclear force?


  it can hold nucleons together when they are separated by up to about 3fm(x10^-15)
• why is the strong nuclear force repulsive up to about 0.5fm(x10^-15)?


  otherwise there would be nothing to stop it crushing the nucleons to a point
• what can you say about the size of the strong nuclear force whether it's p-p, n-n or n-p?

  it is the same as it works equally between all nucleons
• how were neutrinos discovered?


  it was observed that energy after beta decay was less than before, conservation of energy means a particle is responsible for making up the rest of the energy and momentum - the neutrino
• what are the 7 types of EM radiation and how do wavelength and frequency change along the spectrum?


  radiowaves, microwaves, infra-red, visible light, ultra-violet, x-rays, gamma rays. frequency increases down the spectrum, wavelength decreases
• what is the relationship between the frequency and energy of a wave?

  the higher the frequency the greater its energy
• what is a photon and the equation of calculating their energy?

  they are discrete waves (packets which carry energy) energy = (h x C)/wavelength
• what is an anti-particle?

  a particle which has the same mass and rest energy but opposite charge to it's other in the particle - antiparticle pair
• what can you assume about the rest energy of a neutrino and why?

  that it is 0 because their mass is so small
• what is pair production and what is required for it to happen?


  when energy is converted into mass you get equal amounts of matter and anti-matter (this is pair production), it only happens if there is enough energy to produce the masses of the particles
• in pair production why would the two particles produced curve away from each other in an applied magnetic field?

  because they have opposite charges
• what is the minimum energy needed for pair production?

  it is the total rest energy of the particles produced (Emin=2E0)
• what happens when a practice meets its antiparticle?


  the annihilate, all mass is converted back to energy in the form of two gamma ray photons (2Ephotons=2E0)
• how is annihilation used in industry?


  in PET scanners - positron emitting isotope put it into the bloodstream and gamma rays produced are detected
• what are hadrons and what are the 2 types?


  they are non-fundamental particles which can feel the strong nuclear force. they are split into baryons and mesons
• what are baryons (with examples) and what do they all decay into and why?


  all baryons are made up of three quarks, for example protons and neutrons. all baryons eventually decay into protons because a free proton is not unstable
• what are mesons and what are the 2 main types?

  all mesons are made up of 2 quarks and are unstable, the two main types are pions and kaons
• what are pions and kaons and name some properties?


  pions are the lightest mesons and are the exchange particle of strong nuclear force.

  kaons are heavier and more unstable, they have a very short lifetime and decay into pions
• how can you detect mesons using cosmic rays?


  cosmic rays interact with molecules in atmosphere and produce 'showers' of high-energy particles (including pions and kaons), they can be detected using 2 Geiger counters separated by absorbing lead. if both counters detect radiation simultaneously then it is likely that's a 'shower
• what are leptons?


  fundamental particles which don't feel the strong nuclear force, mainly interact through weak interaction but also a little through gravitational and electromagnetic
• what are the 4 main types of lepton?

  electrons, muons, electron neutrinos and muon neutrinos (muons are like heavier, unstable, electrons and decay eventually into electrons)
• what 2 lepton quantities need to be conserved in reactions?


  Le - electron lepton number

  Lu - muon lepton number
• how is strangeness created?


  via the strong interaction and strange particles are created in pairs (to conserve strangeness)
• how do strange particles decay and what happens to strangeness?


  through the weak interaction and strangeness in not conserved
• what properties are conserved in an interaction excluding the quantum numbers?

  energy, momentum and charge
• what are the properties on an up and anti-up quark?


  up: charge = +2/3 baryon number = +1/3 strangeness = 0

  anti-up: charge = -2/3 baryon number = -1/3 strangeness = 0
• what are the properties of a down and anti-down quark?


  down: charge = -1/3 baryon number = +1/3 strangeness = 0

  anti-down: charge = +1/3 baryon number = -1/3 strangeness = 0
• what are the properties of a strange and anti-strange quark?


  strange: charge = -1/3 baryon number = +1/3 strangeness = -1

  anti-strange: charge = +1/3 baryon number = -1/3 strangeness = 1
• what are the quark compositions of the 4 types of kaon?


  K+ = us-, K- = su-, K0 = ds-, K0- = sd-
• what are the quark compositions of the 3 types of pion?


  pi+ = ud-, pi- = du-, pi0 = uu-, dd- or ss-
• what are the quark compositions of a proton or a neutron?


  proton = uud, neutron = udd
• why can you not get a quark by itself?


  its just not possible, if you fire lots of energy at a proton the energy builds up until there is enough to make an u and u- couple and make a pi0