Lighting Sources

Within the lighting industry, electric light sources are referred to as lamps, which include bulbs and tubes. Common light sources include:

Incandescent lamps are one of the oldest electric lighting technologies available. Incandescent bulbs produce light by passing a current through a filament, causing it to become hot and glow (also causing waste heat).

Tungsten halogen lamps are slightly more energy efficient and last longer than standard incandescents. One advantage of the tungsten halogen lamp is its controlled beam spread, which makes it ideal for accent lighting. Tungsten halogen lamps can be used in track, recessed, outdoor spot and floodlight settings.

• Fluorescent tube lamps: Fluorescent tube lamps are very commonly used in business applications; these lamps are generally identified as T12 and T8, referring to the diameter of the tube. T12s are 12/8 of an inch in diameter, while T8s are 8/8 of an inch. Typically, T8s are more efficient than T12s.
• Compact Fluorescent Lamps (CFL): CFLs have higher efficacy and longer life than comparable incandescent lamps. CFLs come in a variety of shapes and sizes and are compatible with most fixtures designed for incandescent bulbs.
• Light Emitting Diodes (LED): LEDs are a solid-state light source that delivers a direct beam of light at a very low wattage. LEDs currently have efficiencies comparable to that of compact fluorescent lamps, between 20–60 lumens per watt. Over the next twenty years, however, technology is projected to be able to achieve more than 150 lumens per watt. Although the efficiency of the individual LEDs currently may not be significantly higher than other, conventional sources, the efficiency of the entire lamp and luminaire combination is very high, as nearly all of the light gets directed out of the luminaire.

High-Intensity Discharge (HID) bulbs have a longer life and provide more light per watt than any other light source. HID bulbs are commonly used for outdoor security and landscape lighting. Mercury vapor lamps, which originally produced a bluish-green light, were the first commercially available HID lamps. Today, they are also available in a color-corrected, whiter light. Increasingly, the more efficient high-pressure sodium and metal halide lamps are replacing mercury vapor lamps. Standard high-pressure sodium lamps have the highest efficacy of all HID lamps, but they produce a yellowish light. High-pressure sodium lamps that produce a whiter light are now available, but their efficiency is somewhat lower than traditional high-pressure sodium lamps. Metal halide lamps are less efficient but produce an even whiter, more natural light. Colored metal halide lamps are also available.

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