The Spectrum - Colours of Light

White light split into all the colours by a prism

Simulated image produced by Andy Newsam

The amount of each colour is called the spectrum of the light.

You can see all the different colours using a prism like the one in the picture which uses refraction to split the light up. This works because different colours are bent by different amounts and so they come out of the prism in slightly different directions.

Astronomers often want to know exactly what colours there are coming from a particular star or galaxy. They use special instruments called spectrographs.