P2 Particles and Radiation

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Photons incident on a metal surface cause electrons to be emitted from the surface.

State what is meant by the photo electric effect.

The minimum frequency of electromagnetic radiation that can cause photoelectric emission.

State what is meant by the threshold frequency.

The minimum amount of energy required to remove an electron from the metal surface.

State what is meant by the work function of a metal.

The work function+Max Kinetic energy of photoelectron.

hf=

Low pressure mercury gas.

What substance do fluorescent tubes contain within them?

Electrons are accelerated by a potential differenceand inelastically collide with the mercury atoms.

What causes the mercury, in fluorescent tubes, to release photons?

Electrons within the mercury atom are excited, to a higher energy level, by the collision so kinetic energy is not conserved in the collision.

How do we know the collision between electrons and mercury atoms in a fluorescent tube is inelastic?

It de-excites to a lower energy level producing a photon of a specific frequency proportional to the difference in energy levels (using E=hf). UV.

What happens after the mercury atom is excited?

They are absorbed by the fluorescent coating of the tube and excite electrons within the coating.

What happens to the UV photons emitted from the mercury atoms, in the fluorescent tube?

The electrons of the coating de-excite in stages, cascading down energy levels, emitting multiple lower energy photons. These will have frequencies within the visible range.

How does a UV photon incident on a fluorescent coating produce visible light photons?

the photo electric effect.

Evidence for waves acting as particles include

electron diffraction

Evidence for particles acting as waves include

No

Are the number of particles conserved in every interaction?

Yes

Is baryon number conserved in every interaction?

No

Is velocity conserved in every interaction?

No

Is strangeness conserved in every interaction?

The weak interaction

When may strangeness not be conserved?

Yes

Is charge conserved in every interaction?

Yes

Is energy conserved in every interaction?

Yes

Is lepton flavour conserved in every interaction?

Yes

Is momentum conserved in every interaction?

No

Is mass conserved in every interaction?

Yes

Is lepton number conserved in every interaction?

Strangeness and maybe kinetic energy (eg. if an electron/atom is excited)

What are the only 2 things that may not be conserved in an interaction?

The ratio of charge to mass

Specific Charge

An atom with the same number of protons but a different number of neutrons.

Isotope

0.5fm or less

At what distance does the strong nuclear force become

3fm

What is the maximum range of the strong nuclear force when it is attractive?

nucleons and quarks.

The strong nuclear force acts between

There was an energy deficit in beta decay. (Goes against Energy Conserv)

Why was the existence of the neutrino hypothesized?

The beta particles are emitted with a range of kinetic energies.

What data suggested that energy is unevenly/randomly distributed between the products of beta decay (assuming conservation of momentum)?

carried away by the neutrino.

When the kinetic energy of the beta particle is less than its maximum value, the rest of the energy (the deficit) is

It is very small and uncharged.

What properties of the neutrino can be inferred based on the fact it hadn't been detected?

Pion

State the exchange particle for the strong nuclear force between nucleons.

The strong nuclear force has a very short range and so the pion will only be able to travel so far and exchange a force.

Suggest why can we hypothesize that pions may decay quickly/have a short lifespan?

The kinetic energy gained by an electron when accelerated from rest from at infinity to a potential of 1V.

Define the electron volt.

When a particle and its antiparticle pair meet and annihilate to produce 2 photons of equal energy travelling in opposite directions.

State what is meant by the term annihilation.

The 2 photons that are produced are travelling opposite directions and have equal energy.

How is momentum conserved when a particle and its antiparticle pair annihilate?

Some of the energy from a photon is converted into mass to produce a particle and its antiparticle pair.

State what is meant by the term pair production.

The virtual poton

State the exchange particle for the electromagnetic force.

W⁺ or W⁻ Boson

State the exchange particle for the weak interraction.

W⁻ Boson

What is the exchange particle in Beta- decay?

What is the exchange particle in Beta- decay?

What is the exchange particle in Beta+ decay?

The transmission of an exchange particle.

In a Feynman diagram for particle interactions, what does the wiggly line indicate?

The progression of Time

In a Feynman diagram for particle interactions, what does the y axis indicate?

The proton as it is catching the electron.

In electron capture, which particle does the W+ Boson emanate from?

The electron as it comes first.

In electron-proton collisions, which particle does the W- Boson emanate from?

W⁻ Boson

In electron-proton collisions, what is the exchange particle?

W⁺ Boson

In electron capture, what is the exchange particle?

A proton within the nucleus captures an inner orbital electron and becomes a neutron.

State what occurs in electron capture.

corresponding antiparticle.

For every type of particle, there is a

Their rest mass.

What is the only property that particles share with their corresponding antiparticles?

They have the same magnitude but an opposite sign.

How do the quantum numbers of a particle differ from its antiparticle?

Quarks

Which family of fundamental particles are subject to the strong force?

Leptons

Which of baryons, mesons and leptons are not subject to the strong force?

Baryons and mesons

What 2 groups are hadrons divided into?

They are made up of quarks.

What is the defining feature of hadrons?

Leptons

Which group of fundamental particles are not subject to the strong nuclear force?

3 quarks (Baryon number of 1)

What is the general quark composition of a baryon and what is it's baryon number?

A quark and a different antiquark. (Baryon number of 0)

What is the general quark composition of a meson and what is it's baryon number?

All of them.

Which fundamental particles are subject to the weak interaction?

All charged particles.

Which particles are subject to the electromagnetic force?

All (but it becomes pretty negligible).

Which particles are subject to the gravitational force?

An electron

What will a muon decay into?

No

Are neutrinos charged?

Proton

What is the most stable baryon?

Kaons

What can decays into pions?

They are strange.

What is the defining feature of kaons?

Kaons and the corresponding antiparticles are produced in equal numbers to maintain 0 net strangeness.

How are kaons produced by the strong interaction if strangeness is conserved?

The weak interraction

Which interaction do kaons decay by?