Particles

What is an exchange particle?

A virtual particle that lets a force act between 2 particles in an interaction.

What is another term for exchange particles?

Gauge bosons.

How can you tell whether it is a Strong or Weak interaction?

If leptons involved and/or strangeness not conserved (0,-1,+1)= WEAK

If hadrons & strangeness conserved = STRONG

What is the difference between electron capture and electron-proton collisions?

In electron capture, a proton within a nucleus captures an electron from the atom, turning into a neutron and also emitting a neutrino.

In electron-proton capture, a free electron is fired at a free proton and collides with it, producing a neutron and a neutrino.

What interaction creates strange particles?

Strong interaction

What are the letters form both Nucleon Number and Proton Number?

Nucleon number: A

Proton number: Z

Explain how radioactive carbon-14 can be used to find the age of a fossil. (3 marks)

• All living organisms have the same amount of carbon-14 atoms as a percentage of all carbon isotopes.

• Once the organism dies, it no longer absorbs carbon from the atmosphere.

• Carbon-14 is radioactive and so will decay over a known half life.

• (The older the fossil is, the fewer carbon-14 isotopes it will contain and the less radiation it emits.)

The distance at which the strong nuclear force becomes repulsive is about what?

• 0.5fm and under

Why was the Antineutrino hypothesised? (5 marks)

• When scientists first observed beta decay, they thought that neutrons were decaying into a proton and an electron only.

• They noticed that the energy of the neutron before the decay was larger than the energy of the proton and electron after the decay: energy was not being conserved.

• To account for this, scientists hypothesised that a new type of particle was being produced and carrying away some energy.

• This particle must have zero (or almost zero) mass and must be electrically neutral (to obey charge conservation).

• This particle was then called a neutrino but we now know it to be an antiparticle called an antineutrino.

What are exchange particles sometimes also called?

• Gauge bosons

What is the exchange particle of the strong nuclear force between quarks?

Pion/Gluon

What do kaons decay into and by what interaction?

• Pions

• Weak interaction with the W+ boson.

What do muons decay into?

• Electrons

Isotope

Atom with the same proton number but different mass number

Specific charge

Charge C / mass kg

What are the four fundamental forces

Strong nuclear

Gravity

Weak nuclear

Electromagnetic

Properties of the strong nuclear force

affects hadron

Exchange particle is pions / gluon

Hold protons and neutrons together

Repulsive at less than 0.5 fm

Attractive up to about 3-4fm

Properties of the electromagnetic force

Affects charge particles

Exchanged by the virtual photon

Causes protons to repel each other

Properties of the weak nuclear force

Affects all types of particles

Exchange particles are the w+ and w- bosons

Properties of gravity

Affects particles with mass

Graviton exchange particle (Not found only theorised)

Attracts nucleons together due to mass

Main types of nuclear decay

Alpha, beta^±

Features of an alpha decay

Alpha particles are helium nuclei usually emitted from very large particles

Proton number decreases by 2

Nucleon number decreases by 4

An alpha particle is emitted

Features of a beta minus decay

Neutron decays into a proton

Emits an electron and an electron antineutrino

The electron is the beta minus particle

The proton number increases by 1

Features of beta plus decay

Proton decays into neutron

Proton decays into a beta plus particle and an electron neutrino

Beta plus particle is a positron

Proton number decreases by 1

What are photons

Discrete bundles of electromagnetic radiation

Planks constant equations for energy

E=hf=hc/λ

h is planks constant 6.63×10-³⁴

What is antimatter made up of

Antiparticles (Same mass, opposing charge)

What is pair production

When a photon has sufficient energy it can be converted into a particle and corresponding antiparticle

What is annihilation

When a particle meets its antiparticle, converting into 2 equal energy photons that move in opposite directions

What is a hadron

Non fundamental particles that feel the strong nuclear force

Baryons and Mesons are Hadron

Protons are most stable baryon

Baryon number must be conserved in interactions

What are leptons

Fundamental particles such as electrons muons and neutrinos (And Tauon)

Neutron decay

Neutron decays into a proton electron and electron antineutrino

Quarks

Fundamental subatomic partial making up hadrons

Up down and strange are 3 flavours

What is a baryon

A combination of 3 quarks or antiquarks

Proton uud

Neutron udd

Mesons

quark and an antiquark

Conservation laws

Energy

Momentum

Charge

Baron number

Lepton number (Split in to muon and electron numbers)

Strangeness is conserved in strong interactions

Kaon composition

K⁺ uS̅

K⁰ dS̅

K^- sū

Pion composition

n⁺ uđ

n^- dū

n⁰ uū dđ