Encyclopedia Article

# Light - Research Article from Macmillan Science Library: Mathematics

This encyclopedia article consists of approximately 4 pages of information about Light.
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Light is a form of electromagnetic radiation. Other types of electromagnetic radiation include radio waves, microwaves, infrared, ultraviolet, x-rays, and gamma rays. All electromagnetic waves possess energy. Moreover, electro-magnetic waves (including light) are produced by accelerated electric charges (such as electrons). Light moves through space in a wave that has an electric part and a magnetic part. That is why it is called an electromagnetic wave.

## Speed of Light

Light travels through empty space at a high speed, very close to 300,000 kilometers per second (km/s). This number is a universal constant: it never changes. Since all measurements of the speed of light in a vacuum always produce exactly the same answer, the distance light travels in a certain amount of time is now defined as the standard unit of length. For convenience, the speed of light is usually written as the symbol, c.

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