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Rainbows have a special magic, don’t they? They have the most awesome power to surprise, delight and inspire us.
And I’ve never met a child who didn’t marvel at that arc of colours in the sky when it appears.
BUT children almost just accept rainbows as something magical. Heck, us adults do too!
BECAUSE we all struggle to get our heads around the physics behind them.
I mean, how can all those colours in a rainbow appear from transparent light?
It can kind of defies our common sense understanding of the world, doesn’t it?
So this year, we’ve been loving this simple experiment for making our very own rainbows. They’ve delighted us but also let us see for ourselves physics in action.
And you can do the same for fun at home or in a classroom or home school lesson plan.
And for more simple activities to explore nature with kids do check out my other nature notes.
1. Rainbow Making Supplies
To make your rainbows you need nothing more than a basic prism. The five little ones in the video below cost us just £5 (roughly $5).
You may even be able to make do with some dangly earrings or bits of old light fittings.
And so much the better if you can because this helps children see science is all around us.
2. Make Your Own Rainbows
This experiment is so simple, it barely feels like an experiment. But WOW it’s powerful!
We simply hung 5 little prisms in a sunny window … and waited for the sun to shine …
And when it does, we have rainbows.
Lots of them.
We have rainbows dancing around the door frame as we come up the stairs …
We have rainbows on the wall …
And rainbows on the ceiling …
We even get rainbows on the floor!
And through those little prisms, we can actually see what’s going on. And start to understand not only what makes a rainbow …
… BUT also, something very cool about the fundamental properties of light!!
3. What Makes A Rainbow?
Our little prisms helped us see that white light is actually made up of a range of colours. That range of colours is what we call a spectrum.
When waves of light from the sun hit the prism – or a raindrop – they are bent. Or as it is called technically in physics refracted.
BUT different colour light waves are bent different amounts:
- Violet light bends the most.
- Red light bends the least.
So when light shines through a prism, the very bendy violet light emerges at a different point than the not so bendy red light.
And we can see the separate colours …
All the seven colours of the rainbow bend slightly different amounts because they all have different wave lengths.
- Each violet wave is shorter than the other waves and that’s why violet light bends more. And is at one end of the rainbow.
- And each red wave is longer than the other waves and that’s why red light bends less. And is at the other end of the rainbow.
So that beautiful great arc in the sky actually appears when different coloured waves of light are bent different amounts through raindrops, depending on how long their waves are.
It’s still pretty magical isn’t it?
But understanding light is made up of different coloured waves of different lengths is a super powered building block for children to understand the physics of light and colour.
How cool is that?
And I’ve got lots more light and colour experiments for you here including telescopes, kaleidoscopes, shadows and sunsets.
I hope you enjoy them as much we do.