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LED

Convenient Uses And Ambitious Plans

LEDs show an immunity to electromagnetic interference, power surge hazards, and changes in temperature. Red LEDs are sturdy, bright enough without being too hot, and cheap enough to be conveniently used in place of more common white light sources. Green ones are used to light up phone keypads, for instance. As circuit board indicators on personal computers, they can withstand the heat stress of active integrated circuitry. LEDs also show up on electronic newscasters, are used on a large scale on building exteriors but are also available in portable forms. Laptop computers use LEDs to create the equivalent of a 12-inch monitor on a much smaller scale. Long distance phone service is renewed at switchers and loop circuits, and cable TV transmissions are aided at relay stations with a combination of lasers and LEDs known as optical coupling. LEDs provide the stimulated emission of radiation required for onset of laser action in these fiber-optics applications. AT&T/Bell Labs has produced the basic LEDs for full-color reproduction-red, green and blue (RGB)-from the same material. An array of LED-supported colored lasers might produce a new kind of television set in the future.

Resources

Periodicals

Clery, Daniel. "After Years in the Dark, Electric Plastic Finally Shines," Science (March 25, 1994): 1700-02.

Keenan, Tim. "New Hewlett-Packard LED turns on the Brights," Ward's Auto World (March 1994): 126.

Marston, Ray, "Working with LEDs," Radio-Electronics (February 1992): 69.

Jennifer Kramer

KEY TERMS

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Dopant

—A chemical impurity which is added to a pure substance in minute quantities in order to alter its properties.

Electroluminescence

—A luminous discharge of high frequency brought about by photon emissions.

Rectifier

—A device that converts alternating current (AC) to direct current (DC).

Semiconductor

—A solid whose conductivity varies between that of a conductor (like a metal) at high temperatures and that of an insulator (such as rubber) at low temperatures.

Solid-state

—Refers to the exploitation of the electric, magnetic, or light-producing capabilities of solids without depending on electron tubes.

Additional topics

Science EncyclopediaScience & Philosophy: Laser - Background And History to Linear equationLED - The Solid-state Lamp, Convenient Uses And Ambitious Plans