White Light
Create a colour wheel to demonstrate the components of white light.
What You Need
Materials per student
- 1m of string
- Six different pieces of coloured paper (red, blue, yellow, green, orange and purple)
- Scissors
- Glue
- Pencils
- Toothpick
- Wheel Template
Guide:
Safety Notes
Ensure you are familiar with Let's Talk Science's precautions with respect to virtual outreach to youth.
What To Do
To make the colour wheel, each student will:
- Trace the triangles from the template onto each coloured paper.
- Glue the pieces of coloured triangle onto the corresponding colours on the wheel.
- Cut out the wheel and poke holes where indicated on the template carefully with a pencil or toothpick.
- Thread the string through each hole and tie the ends of the string together.
- Gently move the wheel so that it is in the middle of the string.
Experiment
- Holding both ends of the string, have students swing the circle 20 times so that the string is twisting.
- Instruct students to pull their hands apart so the string is tight. The wheel should be spinning very fast. If they move their hands closer together and the string should twist up again. They can repeat this process until they have a good rhythm (it may take a few tries, but it should make a whirring sound if it is working).
- Look at the spinning wheel, what colour(s) do they see?
Discovery
Natural light is made up of many different colours. If we slow this light down by making it pass through a prism (or water droplets in the case of a rainbow), it will break up into different colours. The opposite is also true when we have separate colours and make them travel together quickly - our eyes will see them as one colour. If we used all the colours of the rainbow on our wheel and made it spin really fast, it would appear as white.
What's Happening?
Natural light is made up of many different colours. If we slow this light down by making it pass through a prism (or water droplets in the case of a rainbow), it will break up into different colours. The opposite is also true when we have separate colours and make them travel together quickly - our eyes will see them as one colour. If we used all the colours of the rainbow on our wheel and made it spin really fast, it would appear as white.