What are gamma rays?

Gamma rays are high energy electromagnetic waves given out by the nucleus of radioactive elements. In a sense they behave like very energetic light waves but we can't see them because their wavelength is too short.

Gama rays are electromagnetic waves with very short wavelength. They result from the decay of radioactive elements

Gamma rays are waves, just like light is a wave. In fact, you could say that gamma rays are a type of "invisible light". The difference is that the wavelength of gamma rays is much shorter than visible light. That means that gamma carries more energy than visible light, which makes it dangerous. Since this is posted as a KS3 question, we will just say that gamma rays can kill your cells or give you cancer (if you are unlucky). They can also be useful for killing germs (sterilisation) or for killing cancer cells. They must be carefully aimed to do this!

At GCSE level, we need to explain that gamma can knock an electron out of an atom. This is called ionisation. If the ionisation happens in one of your cells during cell division, it can change the instructions for the new cell. This can cause the cell to produce many more copies of itself, which is harmful. This is called cancer. Gamma is not as ionising as alpha or beta. This means it does not give up its energy as easily so it can travel through more substances. It is more penetrative. Gamma has the shortest wavelength, and therefore the highest frequency, on the electromagnetic spectrum (the "family" of waves which includes light).

At A Level we would need to go deeper than an answer which can be given here. We start to think of gamma as a high energy particle of light (a photon) rather than a wave. We can calculate the attenuation co-efficient, discuss how gamma can convert to other particles and antiparticles or explore its uses in medical physics. Plus lots more...