These early light bulbs produce light by heating a filament wire to a high temperature until it glows. As the light is produced by heat, a large amount of energy is wasted making them very inefficient.
Compact Fluorescent Lamps
In a bid to reduce the amount of energy wasted through heat, the CFL lamp was born. These early energy saving lamps contained a combination of argon and mercury gasses which, when excited by electricity, give off invisible ultraviolet (UV) light which excites the florescent (phosphor) coating, giving off visible light.
The most recent form of lamp, far exceeding the previous two in efficiency, is the LED (Light Emitting Diode). LEDs are illuminated by the movement of electrons in a semiconductor. LEDs emit a blue light that, though use of a phosphor coating can produce any colour temperature. Due to the lack of a filament LEDs can surpass incandescent bulbs not only in terms of efficiency but in lamp life as well, by tens of thousands of hours.