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Thursday, July 10, 2008

The sun's spectrum

Lay a piece of white paper on the windowsill and piece on it a polished whisky glass full to the brim with water. Fix a postcard with a finger-wide slit onto the glass, so that a band of sunlight falls onto the surface of the water. A splendid spectrum appears on the paper, and the bands red, orange, yellow, green, blue, indigo and violet can be easily distinguished.

The experiment is only possible in the morning or evening when the sunlight falls obliquely. It is refracted at the surface of the water and the side of the glass and is separated as well into its coloured components. The experiment also works well with light from an electric torch.

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