Unlike an incandescent bulb where a filament is heated to generate light,
light is emitted in a LED when electrons, excited from their chemical
bonds by electrical energy from a battery, re-form these bonds, releasing
the energy as light. The process of emitting light from an LED is more
rapid and more efficient than in the incandescent bulbs where most of
the energy is wasted as heat. The high efficiency, fast switiching times,
and low heat output of the LED have led to many new applications.
By varying their atomic compositions, light emitting diodes (LEDs) of
any color can be made.
Red, green, and blue light are the primary colors of additive color
mixing. Varying amounts of these three colors of light can be added to
create the other colors of light in the visible spectrum. Color televisions
and computer monitors use this red-green-blue (RGB) additive color mixing
scheme to create their images. (In contrast, paint and ink pigments rely
upon subtractive color mixing of the yellow, cyan, and magenta primary
colors.) We are grateful for design contributions from Tom Braniak, Trish
Ferrett, and Mike Condren.
An LED traffic light in Wisconsin. This one still has an incandescent yellow light. Larger movie in a new window
