The seven colours

Before Newton, nobody knew that visible light was made up of seven colours. People thought that light was just ‘light’ and that colours were a mixture of light and darkness. They thought that bright red was ‘light’ with just a little bit of ‘darkness’ and that deep blue was pretty much all ‘darkness'. But... they were wrong!

Have you ever seen a small rainbow on a wall in your house or school? This is formed when light is bent (refracted) through a prism (a glass object with flat, polished surfaces).

The prism causes the visible light to bend or refract. The violet light is bent more than the red and yellow light, so the colours separate. These colours - all the colours of the rainbow - make up visible light.

Visible light bent (refracted) by a prism

Newton used a prism to split light into the colours of the rainbow and project the rainbow on to a wall. To prove that the prism wasn't colouring visible light, he then used another prism to refract or bend, the light back together again.

This caused all the colours to merge together into what we call visible or white light. Pretty impressive, right?

Newton's colour wheel

A similar thing happens when you spin a Newton colour wheel.

When the colour wheel spins rapidly, the colours merge into each other very fast and our brain is not able to distinguish between the different individual colours. So, what do you get when all the colours of the rainbow are merged together? White (or visible) light!

Why not make the colours of the rainbow disappear with a Newton colour wheel and amaze your friends and family?

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