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Description

We are going to find out what happens when the colours of the rainbow spin very quickly. Making a rainbow spinning top.

Resources

1 basswood circle
Pre-cut coloured paper triangles
1 glue stick
1 kebab skewer
A pencil or pen
A small piece of modelling clay or reusable adhesive to protect the sharp end

Instructions

Arrange your coloured triangles in this order:
? Red
? Orange
? Yellow
? Green
? Blue
? Indigo
? Violet
If you have extra triangles, begin the rainbow order again.

Before you start
The kebab skewer may have a sharp point.
Carry it carefully with the point facing down.
Do not wave, throw or point the skewer at anyone.
An adult will help you put the skewer through the wooden disc.

Instructions
1. Find the middle
Place the basswood circle flat on the table.
Find the small hole or centre mark made by your leader.

2. Practise the rainbow
Place the paper triangles on the wooden circle.
Arrange them in rainbow order:
Red → Orange → Yellow → Green → Blue → Indigo → Violet

Do not use glue yet!

Check that:
The pointed ends meet in the middle.
The wide ends follow the curved edge.
There are no large gaps.
The colours are in the correct order.
Ask a friend or leader to check your rainbow.

3. Stick down the triangles
Pick up one triangle at a time.
Cover the back with glue, especially around the edges.
Put it back in the correct place and press it down.
Continue until every triangle is attached.

4. Smooth the paper
Use your fingers to gently smooth each triangle.
Make sure there are no loose corners.
Try not to cover the centre hole with paper. If you do, ask a leader for help.

5. Wait for the glue to dry
Place your disc somewhere safe.
Wait until the glue is dry before adding the skewer.

6. Add the skewer
Ask an adult to help with this step.
Carefully push the kebab skewer through the centre hole.
The disc should sit straight on the skewer—not tilted to one side.
Cover any exposed sharp point with modelling clay or reusable adhesive.

7. Make a prediction
Before you spin the disc, decide what you think will happen.
Will you see:
Separate rainbow colours?
One mixed colour?
A completely different pattern?
Tell your group or write down your prediction.

8. Spin the disc
Hold the skewer between the palms of your hands.
Move your hands in opposite directions to twist the skewer.
Let go with one hand and watch the disc spin.
Keep the spinning disc away from other people’s faces and hands.

9. Watch the colours
Look at the paper while the disc is spinning quickly.
Ask yourself:
Can I still see every colour?
Do the colours look lighter?
Does the disc look white, grey or pale?
Does it look different when it slows down?
Try spinning it at different speeds.

What is the science?
White light is made from many different colours.
When white light passes through a prism or raindrops, it can separate into the colours of the rainbow. A Newton’s disc tries to do the opposite by bringing the rainbow colours back together.
When the disc is still, your eyes can see each coloured section separately. When it spins quickly, the colours move past your eyes too fast for your brain to separate them clearly.
Your eyes and brain blend the colours together, so the disc may appear white, pale grey or a light muddy colour.

This is called colour mixing.

Why might our disc not look completely white?
A handmade Newton’s disc may not produce perfect white. This is normal because:
Coloured paper does not reflect light in exactly the same way as pure coloured light.
Some triangles may be larger than others.
Some colours may be darker or brighter.
There may be small gaps between the triangles.
The disc may not be spinning fast enough.
The lighting in the room can change what we see.

The important observation is that the separate rainbow colours become much harder to see and appear to blend together.

Who was Isaac Newton?
Sir Isaac Newton was an English scientist who studied light and colour more than 300 years ago.
He used a glass prism to show that white light contains all the colours of the rainbow. The Newton’s disc was named after his experiments with light and colour.

Science challenge

Try these investigations:
Spin the disc slowly. What can you see?
Spin it as quickly as possible. What changes?
Look at it in bright light and then in dimmer light.
Ask another person what colour they see.
Compare two discs. Do they look exactly the same?
Remember

Keep the skewer down. Give everyone space. Spin safely.

Tags

• Be creative
• colour mixing
• Colour Spinners
• colour wheel
• experiment badge
• science

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