What Is Black Light?
A very little light that is just visible to the human eye is called black light. The wavelengths of these types of lights fall in high-energy visible light (HEV) range which starts at one extreme end of visible light spectrum. Human eyes detect HEV waves as violet and deep blue. After that, the “black light” or ultra-violet radiations are created as the wavelengths becomes scattered and short which can no longer be detected by the eye.
The wavelengths that can pass through glass are restricted by a fluorescent tube that has an inner coating and it is an example of black light. Same ballast and lightbar can be used by black light as a normal fluorescent light. It is also referred to as “black-blue light” as it shines dimly with a violet or deep blue glow because most of the light emitted from black light is not visible.
A glowing effect is caused as the invisible light is first absorbed by certain pigments and colors and then it is discharged. Its example includes black light posters. UV radiation is also absorbed by the phosphor in a detergent and is then emitted as light, which explains why white socks and shirts shine very much under black light.
Depending upon their wavelengths, black lights can be used for different purposes. Nanometers (one billionth of a meter) are the unit to measure these wavelengths. 100 to 380 nanometers is the range in which the UV spectrum generally falls. This spectrum is divided into the following three categories:
UV-C 279nm – 200nm Short Wave (sterilization, germicidal)
UV-B 314nm – 280nm Medium Wave (forensic applications)
UV-A 380nm – 315nm Long Wave (black lights, entertainment, concerts)
As compared to the red end of visible light spectrum, all UV waves are shorter due to which the terms “medium wave” and “long wave” are relative. Various types of UV devices and their applications also employ these terms to differentiate among them.
For entertainment purposes like in clubs and concerts, a long wave UV-A black light is used. An atmosphere is created in order to make materials glow. Certain body fluids are illuminated by medium wave UV-B rays. So to detect fluids like semen, saliva and blood etc, forensic labs and crime scene investigators employ this type of UV ray. For sterilization of medical equipments and to purify water from living contaminants, a short wave UV-C black radiation is used. It is considered “germicidal” and it has variety of industrial uses.
One should not see directly into black light as it can harm one’s eyes which may be caused due to unseen radiation. UV-protected eyewears with yellow tinted lenses are worn by professionals who work with black lights like UV-C and UV-B. The blue light waves present in HEV spectrum or near to it are blocked by the yellow tint. Experts also believe that occasional exposure to black light as used in entertainment purposes is not harmful. But UV-protected eyewear which includes HEV protection should be worn by those who come in contact with repeated or prolonged exposure.
Category: Technology