as level physics particles and quantum

Cards (42)

  • What is meant by specific charge?
    The ratio of charge to mass: SC = charge/mass (Ckg)
  • Letter associated with proton number?
    Z
  • What is a nucleon?
    A constituent of the nucleus, either a proton or neutron.
  • What letter represents nucleon number?
    A
  • What is an isotope?
    A version of an element with the same number of protons but different number of neutrons
  • Use of radioactive isotopes?
    Carbon Dating
  • What is the strong nuclear force?
    A fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons
  • Range of the strong nuclear 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 nucleons (or both)
  • How do nuclei with too many nucleons decay?
    Alpha decay
  • How do nuclei with too many neutrons decay?
    Beta minus decay, a neutron decays to a proton by the weak interaction (quark change from udd to uud)
  • Why does the neutrino need to exist?
    The energy of particles after beta decay was lower than before, and to solve this problem while conserving charge, the neutrino was hypothesised to carry the excess energy
  • What is meant by beta minus decay?
    When a neutron turns into a proton, the atom releases an electron and anti-electron neutrino
  • What is an alpha particle?
    A particle containing of two protons and two neutrons (like a helium nucleus)
  • What is an antiparticle?
    For each particle, there is an anti-particle with the same rest energy/mass but opposite charge and other properties
  • What happens when a particle and antiparticle meet?
    Annihilation: Mass of the particle and anti-particle is converted to energy in the form of 2 gamma photons (they travel in opposite directions to conserve momentum)
  • What is pair production?
    Gamma photon is converted to a particle-antiparticle pair
  • What are the four fundamental forces?
    Gravity, Electromagnetism, Strong Nuclear and Weak Nuclear
  • Exchange particles for each force?
    Electromagnetic -> Virtual Photon, Gravity -> Graviton, Strong Nuclear-> Gluon, Weak Nuclear -> Bosons
  • What do each of the 4 forces act on?
    Gravity: Particles with mass Electromagnetic: Electrically charged particles Strong nuclear: Hadrons Weak nuclear: Subatomic particles
  • When does the weak nuclear interaction occur?
    When a quark character changes
  • What quantities are considered in conservation laws
    Energy, Charge, Baryon and Lepton number, Momentum, Strangeness
  • What is a hadron?
    Particles that are composed of 2 or more quarks held by the SNF
  • What are the hadron classes?
    Baryons (3 quarks), Mesons (Quark and Anti-quark pair)
  • What force can the pion act as exchange particle for?
    Strong Nuclear Force
  • Why are protons significant?
    They are the only stable baryon, and all baryons eventually decay into protons
  • Strangeness value of a strange quark?
    -1
  • Is strangeness always conserved in a weak interaction?
    Strangeness is only conserved in strong interactions.
  • How are strange particles produced and how do they decay?
    Produced though strong, decay through weak.
  • Are EM waves transverse or longitudinal?
    Transverse
  • What can be used to show that light behaves as a particle?
    The photoelectric effect
  • What is the photoelectric effect?

    When light above a particular frequency (threshold frequency) is shone on a metal, electrons are released (photoelectrons)
  • What is threshold frequency?
    The minimum frequency of light required to eject electrons from a metal surface
  • Why does a photon need a minimum frequency to emit an electron?
    E = hf, the energy of a photon is determined by it's frequency (as h is a constant), and the photon's energy needs to be greater than the work function to emit an electron
  • What is the work function?
    The energy needed to overcome the metallic bonds holding the electron that is to be emitted
  • What should occur when a frequency higher than the threshold is presented by a photon?
    The electron will emit from the surface and the remaining energy is converted to kinetic energy
  • What effect does increasing light intensity have on the photoelectric effect?
    Intensity = more photons per second incident on the metal, each photon however still carries the same energy as before, meaning there is no effect on photoelectric emission.
  • What is the photoelectric equation?
    Energy of a photon = work function + maximum kinetic energy of the photoelectrons
  • What is an electron volt?
    Kinetic energy of an electron that has been accelerated from rest through a pd of 1V
  • How does a fluorescent tube work?
    High voltage applied across mercury vapour accelerated free electrons which collide with mercury atoms, these electrons in the mercury are excited and de-excited, which releases a photon. The tube's coating absorbs the photons and the electrons become excited, and emit visible light photons.