What makes a rainbow?
(Lansing State Journal, July 29, 1992)

Question submitted by:  Nancy Thompson

Ordinary white light, like that from the sun, is made up of many different colors all of which have a different wavelength.  Normally, when we see light from the sun, it appears colorless.  However, Isaac Newton discovered in 1666 that when he passed regular sunlight through a prism (basically, a triangular piece of glass), the prism would split the light up into a band of colors.

The band of colors is called the spectrum which appears in the order of red, orange, yellow, green, blue, indigo, and violet.

When it rains, the air is filled with raindrops.  These raindrops act like a prism.  If sunlight passes through the raindrops at the proper angle it is split into its spectrum, which is made up of the colors of the rainbow.

You can make your own rainbow at home by filling a plastic box with water and placing it near a sunny window.  If the wall next to the window isnít white, place a piece of white paper next to the window.  Next, place a mirror inside the box of water facing the window.  The mirror needs to be tilted towards the sunlight.  The wedge of water in the front of the mirror acts as the prism and the mirror reflects and image of a rainbow on your wall.

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