OCR B: Advancing Physics Chapter 17

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  • Created by: Caraa
  • Created on: 24-05-13 12:36
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  • Probing Deep Into Matter
    • Key words and definitions
      • See my other resources for a full list
    • Rutherford's scattering experiment
      • Most alpha particles went straight through
        • Atoms are mostly empty space
      • Some were deflected back at significant angles
        • So the center of the atoms must be tiny but contain a lot of mass
      • Alpha particles were repelled
        • We know they are positive, so this means the nucleus must be too
      • Atoms  are neutral over all
        • Therefore there must be something negative outside the nucleus (Electrons)
      • How it was conduced
        • Alpha particles (2 neutrons 2, 2 protons) fired are thin foil of gold atoms
    • Coulomb's law
      • F = (kQq)/r^2
        • Q/q = charge
        • F = force
        • r = distance
      • k = 1/ (4 x Pi x Permittivity of material)
      • Inverse square law applies
      • Forces on q and Q will be equal and opposite
    • Closest approach
      • Closest distance that a particle can get to another particle
      • r (closest approach) = (k.Q.q) / Kinetic energy
        • Q and q are charges REMEMBER to use proton number!
        • Remember about changing eV to Joules
      • k = 1 / (4 x pi x permittivity of material)
    • Conservation laws
      • Momentum
      • Energy
      • Charge
      • Mass
    • Types of particles
      • Particle tree (VIEW MY OTHER RESOURCES)
      • Antiparticles
        • Lepton/ Baryon number sign changed
        • Opposite charge
        • Particle and antiparticle annihilate to make energy. The oppose also works.
    • Decay
      • Beta-minus decay
        • neutron -> proton + electron + antneutrino
    • Particle accelerators
      • Linear
        • Alternating current applied to electrodes
          • Timed so that particles are always attracted to the next electrode
      • Cyclotron
        • Circular
        • Two semicircular electrodes used to accelerate particles across a gap.
          • Alternating p.d applied
            • Magnetic field used to keep them moving in a circle motion
              • Particles spiral outwards
      • Synchrotron
        • Circular
        • Electromagnets used
    • Relativity
      • For particles at high speeds
      • No particle that has mass can move equal to or faster than light
      • Rest energy = m.c^2
      • Relativistic factor = Total energy / rest energy
    • Electron energy levels
      • Electrons in an atom can only exist at certain energy levels
      • They can more down an energy level by emitting a photon

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