OCR B: Advancing Physics Chapter 17
- 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
- Most alpha particles went straight through
- 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
- F = (kQq)/r^2
- 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
- Beta-minus decay
- Particle accelerators
- Linear
- Alternating current applied to electrodes
- Timed so that particles are always attracted to the next electrode
- Alternating current applied to electrodes
- 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
- Magnetic field used to keep them moving in a circle motion
- Alternating p.d applied
- Synchrotron
- Circular
- Electromagnets used
- Linear
- 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
- Key words and definitions
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