As the efficiency of electric lighting has improved over the last 150 years it has progressed from carbon, tantalum, osmium and tungsten filaments through gas discharge lamps (mercury, neon, xenon), and now in the 21st century solid-state lighting will have the impetus for the foreseeable future. Even though fluorescent lamps have now achieved 100 lumens per watt, this value was recently matched by a low-power, phosphor-coated blue LED.
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