In the present era of globalization, the world has embraced many path breaking technologies. Amongst them, illumination technologies have come up in a big way, which eventually led to the invention of black light technology. A Black light bulb generally is called as an ultraviolet light or a woods lamp. This acts as an illumination source that emits ultraviolet radiation in the long wave range with very little visible light. A black light lamp basically refers to a lamp that contains a dark blue optical filtering material in the outer coating of the bulb which is made of glass and it blocks most of the light. So the lamp emits ultraviolet radiations. The radiation is invisible but a certain fraction of it passes through the filtering material having wavelengths within range of 400-410 nm. When the lamp is operated it emits a dim purple or a violet glow.
Black light bulbs are made with same technology using which normal florescent lights are made. The only difference being a separate phosphor is used in the inside of the tube which emits ultra violet instead of visible light. The colour of the lamp in the lighting industry is known as ‘black light ‘and the lamps called black light lamps. And as mentioned the black lights are of lower energy, longer waves and does not cause sunburn, though it has the potential to damage vitamins A and D in skin.
Black light sources may be made from specially designed fluorescent lamps or mercury vapour lamps or light emitting diodes or incandescent lamps. In most black light bulbs the blue optical filter material is used to block visible light is in the glass envelope of the night bulb, but in other cases there is a separate filter glass in the lamp housing. In other scientific fields, such as forensics and medicine, such a light source is called as a Wood’s lamp.
Ultraviolet lights have various uses like chemotherapy as a medical treatment and also used extensively in the physics labs, but black lights are essential when ultraviolet lights without visible lights are required like to watch fluorescence. Black lights are also used to decorate indoors using the artistic lighting effects. It even finds extensive usage in the field of medical science. Black light bulbs are most commonly used to give oil paintings, bank notes a real touch. In fact black lights can be used to differentiate between real currencies and counterfeit as legal bank notes have fluorescent symbols which only show under a black light. Besides, the paper used for money printing does not possess any brightening agent which causes commercially available paper to lighten up under black light. Some of these features make illegal notes easily detectable. The same security features can be used in government or corporate identification cards as well.
In medical science such lights are used to detect the presence and extent of disorders that cause loss of pigmentation, like a disease called vitiligo.