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It has been over a century since Thomas Edison invented the incandescent light bulb, but the bulbs most people use today have not changed much in their design and function. The filament in these bulbs becomes so hot from the incoming electrical energy that it begins to glow. Unfortunately 95 percent of that electricity escapes as heat, an extremely inefficient form of lighting.
In fluorescent bulbs, the energy instead flows through gas, and a chemical coating on the surrounding glass tube turns the invisible ultraviolet radiation into white light. Although fluorescent bulbs are at least twice as energy efficient as incandescents, their bluer lighting makes them less desirable for use in homes. - They may be called light emitting diodes, but LEDs have more in common with computers than light bulbs. An LED is a semiconductor diode, which is a solid-state unmoving material that can be changed by electricity. This material is treated to form a positive-negative (p-n) junction. The p-side is called an anode and the n-side a cathode. When the semiconductor is connected to a power source, the electrical current flows from the anode to the cathode. It can only go in this one direction, not the reverse. Energy is released in the form of light.
- LEDs are extremely long lasting. Even after as many as 70,000 hours, they retain nearly three-fourths of their original strength. LEDs are available in several colors, which differ based on the primary materials used to make the diode. Blue LEDs are produced from indium gallium nitride; green is based on aluminum gallium phosphide; and red is from an aluminum gallium arsenide. When all these lights are combined, they become "white" light.
- Compared to incandescent or fluorescent bulbs, LEDs are more uni-directional. This makes them more practical for being placed side-by-side on a strip, for use in darker areas such as staircases, hallways and inside cupboards. It is also possible to purchase waterproof LEDs for outdoor stairways and gardens. In addition, these lighting fixtures are considerably more damage resistant than other lighting options. However, LEDs are very sensitive to heat, which can greatly reduce their light output and longevity.
- As with any new technology, cost is an issue. LEDs have not been used extensively thus far because they are expensive compared to incandescent and fluorescent bulbs; an outdoor LED spotlight, as of 2009, can cost $100, compared to $7 for an incandescent bulb, according to the New York Times (See References 3). Still, the price decreases each year, and LEDs will most likely be a common sight before the decade is over. Even the Empire State Building in New York City is being lit up with these diodes instead of spotlights, which need to be changed too often.
