Most of them went straight through with small deflections, but a small number were deflected through large angles
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Why did some alpha particles deflect at large angles?
Some alpha particles were close enough to the gold nucleus to feel a repulsive force due to the charges of the alpha particles and gold nucleus both being positive
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What did Rutherford conclude from the experiment?
The atom is mainly empty space; There is a tiny central nucleus with orbiting electrons; The nucleus must be charged and contain nearly all of the mass of the atom
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What is thermionic emission?
When a metal is heated so that the electrons gain enough energy to leave the surface of the metal.
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What is thermionic emission used for?
When an electric field is introduced, the electrons emitted form a beam
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Energy of the electrons =
= charge x potential difference = eV
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What is a LINAC?
A linear accelerator
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How do LINACs work?
An AC supply causes the next drift tube to always be the opposite charge of the accelerating ions. Therefore the ions are always repelled from the current tube and attracted to the next tube.
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Why do the drift tubes in a LINAC get longer?
The AC supply has a constant frequency and the ions travel faster after every tube
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What is the setup of a cyclotron?
Two circular electromagnets opposite each other; in between the magnets are two dees with a gap inbetween
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How does a cyclotron work?
Charged particles are accelerated in a circle by the magnetic field; an AC supply causes the other dee to be the opposite charge when the ions are in the gap between the dees
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Which two equations are used to derive the equation for the radius of a charged particle?
F = (mv^2)/r and F = Bqv sin ϴ
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How do particle detectors work?
Ions transfer energy to the medium (usually gas) through which they move by ionisation
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What can be calculated from particle tracks?
Momentum from radius; Charge from direction using Fleming's left hand rule
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What are the relativistic effects on a particle with a very short lifetime?
As the particle is moving at speeds close to c, it experiences time slower so it survives for a much longer time
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1 MeV/c^2 =
1.8 x 10^-30 kg
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1 GeV/c^2 =
1.8 x 10-27 kg
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What must be conserved in particle interactions?
Energy, momentum, charge, baryon number, lepton number
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What happens when matter and antimatter interact?
They annihilate each other and create a photon
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What is particle production?
Photon -> electron + positron
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Other cards in this set
Card 2
Front
What happened to the alpha particles?
Back
Most of them went straight through with small deflections, but a small number were deflected through large angles
Card 3
Front
Why did some alpha particles deflect at large angles?
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