“This charming story can be read on two levels – that of two sisters in search of a physical rainbow and that of emerging from a gloomy emotional episode and beginning to find joy again.  It offers scope for investigating the science of rainbows (as well as instructions for creating one) , but also helps young readers understand that even if siblings or friends don’t like the same things, there are still ways to come together” – Barbara Braxton, Teacher Librarian at The Bottom Shelf in her review of How to Find a Rainbow.

No matter how many times I see them, I always experience a thrill when there’s a rainbow in the sky. They are a true wonder of the natural world, and seem magical even when you know how they’re formed. It’s not surprising to find rainbows in myths and storytelling from around the world, representing a bridge between our world and another, a bow to shoot arrows of lightning, and a sign of God’s promise not to flood the world again. My own children have loved rainbows ever since they were little so I wrote How to Find a Rainbow for them.

If you’re a teacher and you’d like to explore / explain the science of rainbows to your pupils, you may find the following ideas and resources useful. If you’d like to learn more about the science of light or refresh your knowledge of what you should have learned about it in secondary school, you might find my book Why Don’t Things Fall Up? useful.

HOW TO MAKE A RAINBOW:

In How to Find a Rainbow, Reena and Rekha discover something true about rainbows: if you want to see one, the sun needs to be shining brightly from behind you, and water droplets need to be in the air in front of you. You can wait for a day with just the right weather conditions, when it’s rainy and also sunny, or you can make your own rainbow on a sunny day even when there’s no rain. All you need is a garden hose – simply stand so that the sun is directly behind you and put your hose on the spray setting (or put your finger over the end of the hose to make the water spray out) while keeping the sun directly behind you. If you look in the same direction that your shadow is pointing, and a little bit upwards, you should see your very own rainbow! It is literally your own rainbow becauseno two people see the same rainbow – none of us can ever see the “same” rainbow as another person. This is because a rainbow is not something out there in the world in front of us, but something that only exists, in a sense, in our eyes. A rainbow is what we see when sunlight has bounced through raindrops on its way into our eyes. The light that goes into our eyes, cannot go into someone else’s eyes at the same time.

THE RAINBOW SONG IS WRONG!

An interesting thing to point out to your pupils is that the order of colours in it do not match the order in the song “I can sing a rainbow”.

A rainbow is an example of a spectrum, which is the name we give to the colours we see when white light is split up (dispersed) into its constituent colours. This is something that you can show your students with a “rainbow maker” like the one in this video:

You can show your students that, unlike when you mix coloured paints, if you mix coloured light together, you can get white light. You can show them a video or buy a set of coloured torches and do the demonstration yourself.

Image is creative commons, from Wikipedia.

HOW DOES RAIN MAKE RAINBOWS?

Rainbows are formed by the bending (refracting) and reflecting of sunlight when it enters and then leaves a raindrop. There is a nice video explanation for primary aged children on the BBC Bitesize site of the role of rain in how rainbows are formed.

You can show your students some fun demonstrations of refraction and (total internal) reflection using simple apparatus in the classroom.

REVERSING FISH: This demonstration shows refraction – the bending of light as it travels from one medium (substance) to another. You can find a more detailed explanation and a template in the teachers’ notes on this page.:

DISAPPEARING AND REAPPEARING RAINBOW: This demonstration works due to refraction and total internal reflection – you can find a more detailed explanation and a template in the teachers’ notes on this page.:

DISAPPEARING TEST TUBE: Finally, one of my absolute favourite science demonstrations. We can usually see transparent glass objects because, even though they let light pass through them, they reflect back some of the light that shines on them. In this demonstration, the test tube inside the oil “disappears” because light travels at the same speed in the oil as in the glass. This means that light does not speed up or slow down when it travels from oil to glass or vice versa. So, light is not bent or reflected at the boundary between the oil and the glass, meaning there is no light bouncing off the surface of the test tube inside the oil. Detailed instructions and explanation can be found if you click here.