For many people, their knowledge of black light is related to black light posters, which are designed to glow in the dark. However, black light has many more uses, in industries as varied as medicine and banking. In fact, ultraviolet light, which is used in black light products, has been under investigation for more than a century.
History
Robert Wood, a researcher at Johns Hopkins University, invented a filter which would screen out all light which is visible to the human eye. This filter allowed the possibility of ultraviolet photography. Wood also produced the first photographs produced with ultraviolet photography in 1910. However, it would be many more years before the connection was made that the filter invented by Wood could prevent fluorescence from affecting film if placed over a camera lens.
Description of Wood's Lamp
Wood's lamp, which is commonly known as a black light, is an ultraviolet light device fitted with a filter which is opaque to nearly all light rays except those within a specified narrow band. The device is designed to be used in a totally dark environment. It is used to illustrate changes in color and other surface features which are not possible to observe under normal light conditions.
Medical Uses
A Wood's light device is often used in the diagnosis of skin conditions, including sun damage, which can be a precursor to skin cancer. In a darkened room, the medical professional uses the Wood's light on a patient to observe lesions or other changes in the skin surface. The test is painless and noninvasive.
Forensic Uses
Black light technology is also useful in forensic investigations. Old bruises or wounds caused by blows have sometimes been detected by black light technology. Cracks in ceramics and metals which are not visible to the naked eye can also be detected by black light technology.
Uses in Banking
Financial institutions sometimes use black light technology to examine currency which is suspected of being forged. The currency is examined under a black light for inconsistencies. Black light technology is also used to verify signatures.
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