# Particle Physics

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Describe Thermionic Emission
When a metal plate is heated, electrons bubble to the surface and escape
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How does an Electron Gun work
Uses a resistor to heat a plate to produce thermionic emission, and a positive plate used to attract the electrons away from the ions they created
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Describe how to find the Potential Difference that an electron experiences using its velocity
find the kinetic energy ((1/2)mv^2) in eV, by definition this is the voltage the electron experiences
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Describe how protons are isolated for use in particle colliders
Hydrogen gas is passed through a large P.D, electrons attracted to negative plate and protons have been isolated
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Explain how particle accelerators can be used to produce X-rays
Electrons are accelerated, then fired at a metal block, energy is gained, electrons move up energy levels, large drop down means high frequency (X-rays)
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How does a cloud chamber detect particles?
Charged particles will ionise the air, air is supersaturated from low temp, ionisation allow water drops to form which form a visible track
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What distinguishes a Cloud chamber from a Bubble Chamber?
Cloud chamber uses supersaturated air, Bubble chamber uses supersaturated liquid hydrogen
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Describe the discovery of Quarks
High energy electrons are deflected from the outside but occasionally pass through, indicating localized areas of mass and charge
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What is the name and symbol for an antielectron?
Positron: e+
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Why might kinematic equations suggest a particle is travelling faster than light?
They don't account for the increase in mass described the special relativity equation E=m(c^2) hence velocity appears higher
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Why are particles and antiparticles always produced together from energy
Antiparticles have the opposite charge to the regular particle, so charge is conserved (before (energy) =0, after =0)
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How are positrons used in PET scans?
Oxygen-15 injected into blood, decays via positron emission, positron annihilates, photons emitted, emitted photons detected. brain activity shown (more active parts use more oxygen)
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Define 'Baryons'
Particles consisting of 3 quarks or 3 antiquarks
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Define 'Mesons'
Particles consisting of two quarks, a quark and an antiquark
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Observations of rutherfords' experiment
Majority of alphas went straight through, some of alphas deflected by 180 degrees, alphas repelled
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Particles that experience the strong interaction (protons and neutrons)
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What is the Baryon Number?
The number of baryons involved in a reaction
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Define 'Leptons'
Particles that don't experience the strong interaction
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What do all baryons eventually decay to?
A proton, the only stable baryon
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Why are electron-positron pairs the most common to be produced from energy?
They have relatively low mass hence less energy required
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What is the energy source of most particle antiparticle pair productions?
Gamma ray photons
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What is released when a particle-antiparticle pair annihilate?
A pair of gamma rays
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What happens if quark separation is attempted
The energy used to separate quarks to overcome the strong force produces a quark-antiquark pair (meson)
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What four properties are always conserved in particle reactions?
Charge, Baryon Number, Energy, and Momentum
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## Other cards in this set

### Card 2

#### Front

How does an Electron Gun work

#### Back

Uses a resistor to heat a plate to produce thermionic emission, and a positive plate used to attract the electrons away from the ions they created

### Card 3

#### Front

Describe how to find the Potential Difference that an electron experiences using its velocity

### Card 4

#### Front

Describe how protons are isolated for use in particle colliders

### Card 5

#### Front

Explain how particle accelerators can be used to produce X-rays