Alpha, Beta, Gamma
Radiation and nature | Mass | Speed | Range in air | Ionising | Absorbed by | Penetrating | Affected by magnetic field | Uses |
Alpha: Helium nucleus | 4u | 0.1c | 2 - 10cm | Highest | Paper | Lowest | Yes | Smoke alarms |
Beta - minus: electrons | 0 | \frac{c}{2} | about 1m | Mid | Aluminium foil (around 3mm) | Mid | Yes | Radiotherapy, Thickness of metals |
Beta plus: positron | 0 | \frac{c}{2} | N/A | N/A | N/A | N/A | Yes | |
Gamma: photon | 0 | c | Follows inverse square law | Lowest | Several metres of concrete OR Several inches of lead | Highest | No | Radiotherapy, Food irradiation |
Beta-plus is annihilated by an electron
What the radiation can be absorbed by defines how penetrating it is.
Example: Alpha can be absorbed by paper so it is least penetrating.
Ionising is the ability to knock electrons off atoms, turning them into ions. Alpha particle are heavier than beta and gamma and they have a charge of +2 so they lose energy quickly when they collide with other particles.