"We've run these bulbs almost 10,000 hours in test cases, and there's no wear and tear."
Michael Dry
One of the goals of good lighting is to produce a radiation that has an energy distribution very similar to the sensitivity of the human eye. Michael Dry and Charles Wood decided that the ideal radiator would be ionized molecular sulfur (82), which produces a continuous spectrum as opposed to a line spectrum. About 73 percent of the light emission is in the visual spectrum, with only 1 percent in the ultraviolet.
Sulfur plasma is extremely corrosive so normal tungsten electrodes could not be used. Dry and Wood decided to use a magnetron power source rather like those used in microwave ovens, the sulfur being contained in a golf ball-sized quartz bulb. However, the sulfur inside the bulb gets extremely hot and the bulb has to be continually rotated and cooled by a fan to keep it from melting. Another disadvantage was that It was impractical to produce bulbs dimmer than 1,000 watts, and so light pipes or parabolic reflectors had to be used to distribute the luminous energy. The production of commercial sulfur lamps suffers from the fact that the cooling fans are noisy and the magnetrons produce radiation, which can interfere' with Wi-Fi, cordless phones, and satellite radio.
A lamp that completely mimics sunlight remains a dream of the future, but Dry and Wood have continued to develop their bulbs, producing a brighter, more energy efficient, and environmentally friendly light.
