Check out the latest edition of Let's Dive In, where your science questions are answered by Phil and Julie. This one is all about colours and Julie is here to tell us more and explain how you can take part at home!

Who doesn't love a good rainbow? There’s something so magical about them. Red and Orange and Yellow and Green and Blue and Purple! They brighten up everyone’s day.

But where do the colours come from? And what happens if you mix all the colours of the rainbow back together? Does it make black? Or is it white?

That’s our question for this episode, which comes from Erin, Sacred Heart Primary School in Dublin. Her question was: Does black mean no colour, or is that white?

I love a good bit of colour mixing, which is exactly what Phil and I did for this episode. We mixed colours in two different ways to see whether they made black or white.

Before we go into that, we need to understand why we see colours, like the ones in the rainbow! Rainbows are made when sunlight travels through water in the rain and is split into its different parts.

So, if we do the reverse, and add all the different coloured lights together, we will get white light. Adding colours together in this way, is called additive colour mixing.

One experiment you can do for this is to make a colour wheel and spin it around REALLY fast.

To make one of these, you will need:
About one metre of string
Red, orange, yellow, green, blue, purple paints or pens
Scissors - ALWAYS have an adult around when you are using a scissors!

What you need to do:

1) Draw a circle on your paper and divide it into six equal parts.

2) Paint or colour each part in a different colour, ideally in the order of the rainbow.

3) Stick your paper circle onto a piece of card that is the same shape and size of your circle.

4) Poke two little holes into the centre of the wheel and thread your string through both holes to make a big loop, tying the ends together.

5) Hold the string so that you’ve got one end of the loop in each hand.

6) Spin your loopy circle around lots and lots and lots, and then pull the strings tight to see your colour wheel spin really fast!

And watch what happens to your colours! Where did they go?

This is a great example of additive colour mixing: the lights from each colour add together, or merge, or mix, towards white light. You might not get perfect white as you won’t have every colour to mix together, but it will be getting closer to it.

When we take other colourful things, like paint, and mix them together, they don’t behave in the same way as coloured light.

When we see red paint, we see red because the liquid that is the paint is absorbing all the colours except red. It’s like the liquid is a sponge for the red colour: it holds on to all the colours of the light that is hitting it and is only letting the red light back out. And that’s why you see red.

Similarly, if you’ve got green paint, the liquid that we see as green paint is absorbing all the light colours except green, which it lets out. And that’s why you see green.

So, have a go with some paint: what do you think happens if you mix red and green paint? Will it be like the light, where we mix more colours of light together and it gets closer to white?

Why not dive into the paints (maybe not… might get messy!) and this episode of Let’s Dive In to find out? You may also discover whether unicorns are real or not… because you can’t have a chat about rainbows and not mention unicorns!

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And if you have any questions you think we should gab about in future (now that we know where our voices come from) email