Photocopying (Encyclopedia of Science)
Photocopying is the process of photographically reproducing a document of text, illustrations, or other graphic matter. The most common photocopying method used today is called xerography (from the Greek words for "dry" and "writing").
The process of photocopying
The mechanics of photocopying is based on the principle of photoconductivity (when certain substances allow an electric current to flow through them when light is applied). For example, when light is absorbed by some of the electrons (particles that have a negative charge) that make up selenium (a nonmetallic chemical element that is used in the photocopying process), the electrons are able to pass from one atom to another when voltage is applied. When the light source is taken away, the electrons lose their mobility or ability to move.
(The entire section is 642 words.)
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