1. Reminder - using the dispersion of light by a prism to show the visible spectrum

This experiment was described on the Refraction to produce the visible light spectrum notes page.

The higher the frequency and the shorter the wavelength, the more the visible light ray is refracted.

In the 1660s the famous scientist Isaac Newton proved that white light 'contained' all the colours from violet to red. The experiment was quite simple, having dispersed the colours with one triangular prism (left to right in the above diagram) he then used a second triangular prism to recombine all the colours and reproduced the original white light (right to left on the above diagram). That's genius for you - all you have to do is think up a really simple experiment that nobody else had though of!

If you disperse sunlight with a prism or diffraction grating, this is what the solar spectrum looks like.

The wavelengths of visible light range from ~700 nm down to ~400 nm - remember this is only one small part of the whole of the electromagnetic spectrum (EM radiation).