Searching for Surprise Rainbows with SparkLab

Kate, SparkLab Learning Officer, South Bank

Discover rainbows around your home and explore the science of light and colour.

Have you ever noticed a rainbow somewhere that you didn’t expect one? SparkLab Learning Officers have been discovering surprise rainbows all over their homes. This got us thinking… Where do rainbows come from? And how can we create our own rainbows at home?

Search for your own surprise rainbows!

You can explore this too by looking for surprise rainbows around your home. You might find them in the kitchen, in the garden when the sprinkler is on… or somewhere else altogether! What do you notice about the rainbows you find? Are they in dark places or bright places? Do you usually find them at night, in the morning, or during the day? What colours do you see? Where are those colours coming from?

How can we make our own rainbows?

There are lots of ways you can make your own rainbows. Try using objects like a CD or DVD, a big glass of water, or a clear sparkly object. You will also need a little bit of light, next to a little bit of shade. Move your objects around slowly in the light and look very carefully for rainbows. You might want to try moving your object close to the table, the floor or the wall.

  1. Where do you notice the rainbows occurring? What shapes do they make?
  2. What colours and patterns do you notice? Do they always look the same?
  3. What colour is the light that is shining on your object? Is it the same colour as the colours in your rainbow?

Hidden colours: The science behind a rainbow

Rainbows are created when white light gets split up into all its different colours. Sunlight is made up of lots of different colours of light mixed together – we call this white light. When white light passes through some materials, the different colours of light bend – or refract – at different angles. This means that when the light comes out the other side of the material, the different colours of light have split and spread apart. We see this as bands of different colours – a rainbow!

The tiny ridges on a CD or DVD can also split white light up into different colours. As the colours of light bounce off the CD they overlap, which makes some colours appear brighter and cancels other colours out.

Take your exploration further

You can keep experimenting with rainbows using different objects or different sources of light.

  1. What happens if you use a different shaped object, like a square glass?
  2. What happens if you move your object closer or further from the rainbow? How does this change what you see?
  3. What happens if you use a different colour of light? Add a drop of food colouring to your glass of water…what happens to your rainbow?!

Share your discoveries with us!

You can share your discoveries with us! Take a photo of your surprise rainbows, or the rainbows you have created and tag us at #SparkLabQM on Facebook or Instagram.

SparkLab is proudly supported by Academic Partner The University of Queensland.