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About LED Light Bulbs

Author£ºAdmin Hit£º229 Time£º2012/4/6 10:07:41
  • Overview

    About LED Light Bulbs
    About LED Light Bulbs
    Light-emitting diodes (LEDs) are an increasingly popular source of light. Their radiance is not as great as incandescent and compact fluorescent bulbs, but they are more energy-efficient than the former and less toxic than the latter. They are commonly replacing incandescent bulbs in applications where the bulb is viewed--as in stop lights and video displays.
  • Physics of LEDs

    A diode is the simplest type of semiconductor. Semiconductors are poor conductors with impurities added in. The semiconducting material in LEDs is usually aluminum-gallium-arsenide. An impurity is added to half the semiconductor that is a charge carrier. Another impurity is added into the other half of the semiconductor that has near-complete valence shells and is therefore a charge attractor. Placing the semiconductor in a direct current causes a flow of electrons from the charge carriers to the charge attractors. When they bind to the charge attractors, they emit light in a narrow, predictable wavelength range.
  • Less Heat

    LEDs emit much less heat than incandescent bulbs. LEDs emit light because electrons are pushed toward electron receptors, to which they bind. Incandescent bulbs emit light because they are heated enough to be visible, as the sun emits visible light because its surface is heated to 6,000 degrees C by fusion reactions far below. Nevertheless, most of the energy that goes into LEDs, about 80 percent, comes out as heat.
  • A Common Misconception

    Many websites claim that LEDs emit no heat. This is not true. Like any resistor in which electrons are pushed in one direction by an electric field, the acceleration and deceleration of the electrons as they collide with atoms and repel each other leads to heat loss.
  • Color

    Both the sun and incandescent bulbs emit a broad spectrum of light wavelengths because they emit heat (blackbody) radiation from the continuous range of kinetic motion their molecules exhibit. LEDs do not emit light because of a variety of kinetic motion but instead because of one motion--an electron dropping into place with an electron attractor in a pre-determined way. An LED therefore emits at its own wavelength. There are two ways of producing white light, using LEDs. One is to combine three LEDs that produce primary colors. A more common method is to use a phosphor that, when irradiated by the LED, produces a white or whitish spectrum.
  • Vs. Compact Fluorescent

    LEDs and compact fluorescent bulbs (CFBs) have become increasingly popular among those who want to reduce energy consumption from lighting. They both translate a greater percentage of input energy into light than incandescent bulbs do. This can be demonstrated by ones ability to touch either of them after being lit for several minutes, which cannot be done with a conventional bulb comfortably. LEDs and CFBs are both restricted in the wavelengths (colors) they produce. Both use phosphors to broaden their spectrum. CFBs are more radiant than LEDs, which explains compact fluorescents greater popularity. LEDs are non-toxic, while CFBs contain a trace amount of mercury, requiring disposal at a recycling center to avoid groundwater contamination.
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