1 Place the mirror in the glass of water at an angle so that it is leaning against the side of the glass. 2 Put this on the windowsill and turn the glass so that the mirror is directly facing the Sun. 3 Hold the paper at a slant in front of the glass. Move the paper around until you see the rainbow colours. 4 You may need to move the paper around until the colours come into full focus. White light travelling in a straight line appears colourless, but there’s more to light than meets the eye. White light is actually made up of lots of different colours. All the colours of the rainbow, in fact. You have to split white light to see the different colours, and this is exactly what you have done! Raindrops also split light. When sunlight shines though raindrops, the different coloured rays spread out at different angles, and you see a curved band of colours across the sky, which you know as a rainbow. The colour of light depends on how long its waves are, so we see different colours because each colour has a different wavelength. In other words, when we see colours, we are really seeing light of different wavelengths. Red light has the longest waves, orange is slightly shorter, and so on. Violet has the shortest wavelengths.

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