Marvin and Milo

Explore physics the exciting way, by trying out a simple and fun experiment. This month, Electric Slime Don't forget to check back next month for the next edition...

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What you need




Strong glue

Coloured pens

An old CD

A marble



Make a circular shape from the paper using the CD to draw round. Colour it in with the rainbow colours in equal segments.

Make a hole at the centre of the shape, glue it to the CD and stick the marble to the CD through the hole. (Get an adult to help if you use very strong glue.)

Spin the whole thing fast – the colours should turn to white!

Results & explanation


Light of certain wavelengths excites different types of cell in your eyes so you see these inputs as colours. As the CD spins, light reflected from different parts hits your eyes too fast for your brain to tell these apart so you see white light.


Read more about colour vision on


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