Sunlight—bright white light—is a mixture of all the colours of the rainbow. This is called the spectrum of light. The different colours can be seen when a beam is shone through a shaped piece of glass called a prism. The prism bends the light waves. Red waves bend the least, while violet waves bend the most. Raindrops sometimes act as mini-prisms. They split light into the colours of the spectrum. We see them as a rainbow.

Seeing colours

We see colours because some objects reflect different colours of light. Some reflect mostly one colour. Grass, for example, reflects mostly green light, so it appears green. Others reflect a mixture of colours.

Only three, red, green and blue are needed for our eyes to see every colour there is. These are called the primary colours of light. Many different colours can be made by mixing together primary colours in different amounts. For example, red and green together make the colour yellow. Mixing all three together makes white light.