After emitting an alpha or beta particle, the nucleus will often still be ‘excited’ and will need to lose energy.
It does this by emitting a high energy electromagnetic wave called a gamma ray.
Gamma radiation does not consist of particles but as short wavelength, high energy electromagnetic radiation emitted from unstable nuclei.
It is normally emitted alongside alpha or beta radiation.
Gamma ray emission causes no change in the number of particles in the nucleus meaning both the atomic number and mass number remain the same.
It can be written as γ or
Beta and gamma decay of cobalt-60
Properties of nuclear radiations
|Symbol||Penetrating power||Ionising power||Range in air|
|Alpha||α||Skin/paper||High||< 5 centimetre (cm)|
|Beta||β||3 mm aluminium foil||Low||≈ 1 metre (m)|
|Gamma||γ||Lead/concrete||Very low||> 1 kilometre (km)|
All types of radioactive decay can be detected by a Geiger-Muller tube, or G-M tube. The radiations ionise the gas inside the G-M tube and the resulting charged particles move across the chamber and get counted as charges rather like an ammeter.
Key points - alpha radiation
Key points: beta radiation
Key points: gamma radiation