University of Edinburgh
 

BSL Physics Glossary - radiation - example

Radiation is dangerous. We read in the paper about deaths from radiation. I will explain what it is.

There are three different types of radiation: alpha, beta and gamma. The first two are particles: the alpha and beta particles. The third, gamma radiation, is light with a very short wavelength. Gamma radiation can travel through most substances.

Now I have three materials here: paper, aluminium and this very heavy lump of concrete. Alpha particles can't go through paper, but beta particles and gamma rays can. When the three types of radiation hit the aluminium, only the gamma rays get through. Beta particles can get through paper but the aluminium stops them. When gamma radiation hits the concrete the energy is absorbed.

So the concrete stops the gamma radiation from escaping. This is useful in a nuclear power station. The power station is surrounded by a shell of thick concrete. This stops the gamma radiation escaping into the environment. Gamma radiation causes great damage to our bodies. It can travel right through you.

Where do these particles and rays come from? Some materials on earth are radioactive. Radioactive atoms are not stable but they change over time.

An alpha particle is made up of two protons and two neutrons bound together which have escaped from an ordinary atom. It is a bit like a Helium atom without the electrons going round it. Alpha particles are large, heavy and slow-moving particles so when they hit a material like paper, they can't get through.

A beta particle is an electron that has escaped from an atom. It's very small and can travel fast. Beta particles can damage your skin. If you swallowed some of this radioactive source emitting beta particles you would die because it damages your heart and internal organs. So beta particles are much more dangerous to people compared to alpha particles. The alpha particle is slow, whereas the beta particle is small and moves fast. But the beta particles are stopped by a sheet of aluminium.

Gamma radiation is from light and it has the highest level of energy and it is very destructive, but it can't get through concrete.