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An incandescent bulb lights up when electrical power heats a metal filament wire to a high temperature until it glows. You usually get them rated between 15 and 100 watts. Meanwhile, fluorescent lamps (tubes and their newer compact versions, known as CFLs) use inert gases inside to fluoresce and produce light. There are also lamps that use an array of light-emitting diodes (LEDs) working in the way electrons behave, a phenomenon called electro luminescence. Because LED lamps are costly, very few homes use them—and it's best to wait a while before buying for their prices to come down, just as you did with CFLs over the past years. At about 20 a piece, incandescent bulbs may look cheap, but they are not. They waste some 90 per cent of the power consumed—as heat. Consumers preferred them to energy-efficient fluorescent tubes not just because they are cheaper, but also because you may place them in choice lamp shades. Or because the bluish-white illumination from tubes can seem harsh and unnatural, and may contribute to glare and eyestrain. If you don't like the way tube lights look in the hall or bedroom, use them only in passages, verandas and the kitchen.
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