Did you know that sunlight is made up of all the colors? The entire rainbow exists in every ray of sunshine. Using triangular prisms, Isaac Newton was the first to discover the colors that make up white light.
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How does a triangular prism break a sunbeam into different colors? You first have to understand that light travels in waves. Different colors result from different wavelengths of light, which is measured as the distance between two neighboring peaks of each wave. As you can see in the diagram below, out of all the colors of visible light, red light has the longest wavelength, while violet light has the shortest wavelength. White light is a mixture of all the colors of visible light, and "black" is the complete absence of light.
When light moves between two different materials, its speed changes. Certain materials also refract, or bend, the light. When light travels through a glass prism, the prism bends the light. However, as shown in the animation above, the prism bends different wavelengths of light at different angles. This causes the light to separate by wavelength. Though a single beam of white light enters, the prism splits it into all the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet.
Scientists used glass prisms to study the nature of light. Later, designers and artists used crystal prisms so that people could enjoy rainbows in their homes. Many older houses have crystals hanging from lamps or embedded in windows. When the sun strikes them at the correct angle, they cast rainbows on the walls or across the floors.
When it's raining, raindrops can act as tiny prisms if light strikes them at the correct angle. The dramatic result is a rainbow streaking across the sky. The droplets that make up the mist surrounding waterfalls, the spray of sprinklers, and the dew on early morning grass can also act as prisms. Keep your eyes open, and you may have the chance to see what sunlight is really made of.
See for yourself: http://www.youtube.com/watch?v=gtgBHsSzCPE
Watch the following videos to learn more about the refraction and decomposition of light through a prism.