There are lots of ways to make the spectrum colours appear. Here is a really simple one.
You will need
A sunny day!
A white wall
A small mirror
A shallow dish
Put some water in a shallow dish. Prop up a small mirror in the water at an angle.
Place the dish near a window and position the mirror so that sunlight hits it.
The light passes through the water and bounces off the mirror, making a faint rainbow appear on the wall. The white light from the Sun is diffracted (split up) making ‘the colours of the rainbow’ appear in the correct order: Red, Orange, Yellow, Green, Blue, Indigo, Violet. Scientists call these colours the Visible Spectrum.
You could ask the children to make up a phrase using the first letters of each word. This is fun and helps everyone remember the right order. The old one you may know is Richard Of York Gave Battle In Vain – but why not come up with something fresh and original?!
If you do not have white walls, take a large piece of white card and hold it in front of the wall. Adjust it until you can see the Visible Spectrum.
Thanks to, and adapted from lovemyscience.com