LED Technology — Scientific Principles

Scientific Principles

Explain the light source

In a suitable LED, electron–hole recombination emits photons. The device does not rely on a filament heated to incandescence. White lighting can combine a blue emitter with phosphor-converted light or combine differently coloured emitters. White appearance does not correspond to one white wavelength.

Keep three quantities separate

Watts describe electrical power. Lumens describe luminous flux. Lux describes incident lumens per square metre. Two lamps emitting 900 lumens at nine and fifteen watts have efficacies of 100 and sixty lumens per watt. If 600 lumens actually fall uniformly on two square metres, average illuminance is 300 lux.

Measure the complete unit

Drivers, optics and thermal design affect a finished luminaire. A high emitter efficacy is useful evidence but is not the same measurement as complete-unit efficacy or useful illumination at a desk. LEDs still produce waste heat, even though their light does not come from a glowing filament.

Compare equal services and operating time

At five hours a day for 200 days, a six-watt difference amounts to six kilowatt-hours. This assumes the stated equal light output and operating time. Colour temperature describes appearance rather than casing temperature; colour rendering concerns how objects appear. A lighting choice therefore needs the required service and quality as well as an efficient power-to-light ratio.