Ultraviolet lights are used for collecting and for illuminating displays of fluorescent specimens.   They generally consist of a power supply, UV bulb, mechanical enclosure, and a UV filter.   Bulbs and filters are selected for best operation in a specific portion of the UV spectrum.   Power supplies are designed to operate from house current and/or from a battery pack.   Specifications vary widely among different manufacturers.

The most common UV bulbs are similar in operation to fluorescent bulbs used in office lighting systems.   They contain a low pressure mercury vapor.   Striking an electric arc through the bulb produces light which is mostly shortwave ultraviolet, but includes some middlewave UV, longwave UV and visible light.

In a fluorescent bulb for office use, the tube is coated on the inside with a material that fluoresces white.   Thus the UV is mostly converted to visible light and passes through the glass tube.   The glass tube itself blocks all the shortwave UV.

A longwave UV bulb is much the same, except the material coating the inside of the tube is made to fluoresce in the longwave UV portion of the spectrum.   But since the coating also emits a fair amount of visible light, an external filter is needed to block it.   Only a dim purplish glow usually remains.

In a shortwave UV bulb, no fluorescent coating is used, but the tube must be made of quartz or a special glass which allows shortwave UV to pass through.   As above, a filter is added to suppress any visible light.   The modest amounts of middlewave and longwave UV produced by the mercury vapor also pass through the tube and filter, amounting to about 7% of the total radiation produced.   Filters age with exposure to UV and will eventually 'solarize' and begin to block shortwave UV.   It used to be that shortwave filters were rather expensive and lasted only about 500 hours, but a newer kind of filter, introduced about 1980, has extended the useful life by a factor of 10.

Lights equipped with shortwave bulbs, without a filter, are used by doctors to kill germs and by the electronics industry to erase EPROM memory chips.