Particles and Radiation

Word used for a proton OR a neutron in the nucleus

Atoms with the same number of protons and different numbers of neutrons

Proton number

Nucleon number

The charge of a particle divided by its mass (unit: C kg -1)

It overcomes the electrostatic force of repulsion between the protons in the nucleus and keeps the protons and neutrons together

3-4 femtometers

From 3-4 fm down to 0.5 fm

Below 0.5 fm (to prevent neutrons and protons from being pushed into each other

Alpha particles with two protons and two neutrons each

Fast moving electrons

An antineutrino

Electromagnetic radiation

• An electric wave and magnetic wave
• Travelling at right angles to each other and the direction they are travelling (transverse wave)
• In phase with each other

A small burst of electromagnetic waves

6.63 x 10 ^ -34 Js

• A stable isotope is placed, in solid or liquid form, in the path of a beam of protons.
• Some of the nuclei in the substance absorb extra protons and become unstable positron-emitters

1928 by Paul Dirac

A photon with enough energy interacts with a large nucleus or an electron and is converted into a particle - antiparticle pair

Joules/eV

1.6 x 10-19 J

2 x 0.511 (rest energy of an electron) = 1.022 MeV

The reason the electromagnetic force acts between two particles. It is virtual because it cannot be detected

The force involved in ß- or ß+ decay. It is weak as it does not effect stable nuclei

• Non-zero rest mass
• Very short range (no more than 0.001 fm)
• Positively or negatively charged

• Produces a proton and an electron(ß-)
• Exchange particle is W-

• Produces a neutron and a positron (ß+)
• Exchange particle is W+

Neutron decays into a proton and a W+ exchange particle to an electron (ß-) and antineutrino

Positron decays into a neutron and a W+ exchange particle to a ß+ and neutrino

A proton in a proton rich nucleus turns into a neutron through the weak interaction with an inner - shell electron from outside the nucleus

• A proton and electron become a neutron and neutrino
• Exchange particle: W+

• Pions
• Muon and an antineutrino
• Antimuon and a neutrino

• A muon and an antineutrino
• Antimuon and a neutrino

High energy photons

An electron and an antineutrino

A positron and a neutrino

• Protons
• Neutrons
• Pi mesons
• K mesons

• Electrons
• Muons
• Neutrinos

• Weak interaction
• Gravitational interaction
• Electromagnetic interaction (if charged)

• All four fundamental forces
• Strong and electromagnetic interaction if charged

Weak nuclear force

Protons and all other hadrons that decay into protons

Hadrons that do not include protons in their decay products

A particle that decays into pions only

A particle that decays either in sequence or directly into protons and pions

down-anti strange

up-anti strange

down-anti up

• up-anti up
• down-anti down
• strange-anti strange

up-anti down

strange-anti up

strange-anti up

uud

udd

Contains a strange quark