Deceptive CD

What you need

• Paper
• Scissors
• Strong glue
• Coloured pens
• An old CD
• A marble

Instructions

1. Make a circular shape from the paper using the CD to draw round. Colour it in with the rainbow colours in equal segments.
2. 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.)
3. Spin the whole thing fast – the colours should turn to white!

Results and 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.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.