Making rainbows

I mentioned recently that we had been studying rainbows and also that we had made one. Here's how.

You will need:

# A piece of white paper, A4 size
# An open bowl (we used a plastic salad bowl)
# A rectangular mirror
# A lump of old placticine (you will have to throw it away after the experiment as it turns very gooey)
# Water
# Strong sunlight

Method:

1. Fill the bowl with water almost to the top.
2. Place the placticine along the base of the mirror and place the mirror in the bowl, resting on the side at a 45º angle. (The plasticine is to stop the mirror from slipping in the bowl but you may find that you need to use a little more on the edge of the bowl to keep the mirror in place.)

3. Position the bowl so that the mirror catches direct sun light. !!Be careful there is nobody looking at the mirror as you do this!!

4. Now move the white paper so that it catches the reflection of the mirror. This might take a few moments to achieve. It is here where you will see the light refracted, or, in other words, your rainbow.

  

It wasn't easy to take this photo, because of the light differences but you can get a basic idea of what to expect. 

Here is a diagram of how it works

The ray of white light falls from the sun and enters the raindrop. As it passes through the drop the ray decomposes into the seven colours that we so well know. It then bounces off the back of the drop, travels again through, to leave the drop at the front. This, plus millions and millions of other drops the same, is what we see in the sky as a rainbow. The more drops, the stronger we see the colours.