Observing nuclear radiation
A radioactive substance contains unstable nuclei.
An unstable nucleus becomes stable by emitting radiation.
There are 3 main types of radiactive substance -alpha, beta and gamma radiation.
Radioactive decay is a random event - we cannot predict or influence when it will happen.
Alpha, beta and gamma radiation
Alpha radiation is stopped by paper or a few centimenters or air.
Beta radiation is stopped by thin metal or about a metre of air.
Gamma readiation is stopped by thick lead and has a unlimited range in air.