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Make a rainbow with water and a mirror

Suitable For

Grade 4



Time Required

 <12 Hours



What’s it about?

Sunlight or electric light is called ‘white light’, because it appears to be colourless. The reality is that ‘white light’ is made up of a mixture of different colours called a ‘spectrum’, when broken up. These colours can be observed when white light passes through a transparent substance, such as water or glass.

A ‘spectrum’ consists of the seven colours of the rainbow: red, orange, yellow, green, blue and violet – as well as two other invisible colours called: ultra-violet and infra-red. Isaac Newton used a ‘prism’ to split up white light into different colours. In this science experiment we will use water and a mirror to do the same:

Topics covered

White light, Spectrum, Prism, Refraction, Isaac Newton

What will I need?


Procedure (Method)

Unfortunately, this section is only available in the e-book version of the project.

How does it work?

Unfortunately, this section is only available in the e-book version of the project.

The science experiment works because the wedge of water between the mirror and the surface of the water acts as a prism, and splits up the light so you can see all the different colours that it is made up off. This happens because each of the various colours that white light is made up off, travels at a slightly different speed and is bent or ‘refracted’ inside this ‘prism’ by a different amount. Violet light bends the most and red light bends the least, thus a ‘spectrum’ of light is formed on the white cardboard.

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