Ultraviolet (UV) light refers to the electromagnetic radiation that possess a shorter wavelength compared to the visible light and longer than that of the x-rays. The wavelength of UV light ranges from 400 nm to 100 nm (NASA, 2013). This corresponds to photon energies that range from 3 to 4 eV. The UV light got its name from the fact that the spectrum that is formed by the light has electromagnetic waves that have a frequency greater that the ones that are identified by humans as violet. The frequencies are not visible to humans other than those who have a condition called aphakia.
The discovery of UV light was done by a German physicist known as Johann Ritter in the year 1801. The discovery is associated with the observation that was done of the darkening of the silver salts when they were exposed to sunlight. Johann made the observation that the darkening could be associated with the invisible rays that are outside the visible spectrum just after the violet end. The rays were able to darken a paper soaked in silver chloride at a faster rate compared to the violet light (NASA, 2013). Johann called these rays oxidizing rays a name that aimed at emphasizing the chemical reactivity and differentiating the form of light from the heat rays that were discovered one year earlier. Shortly after, the term chemical rays were adopted and retained its popularity throughout the century. The term chemical ray was later dropped, and the term ultraviolet adopted (Hockberger, 2002).
The sun is considered to be the major natural source of ultraviolet radiations which are emitted at all wavelengths. Another natural source of ultraviolet light is the stars especially the extremely hot ones. The development of ultraviolet light from the sun occurs as a result of emission by the electric arcs. Development of ultraviolet light may also result from specialized lights which include black lights and the mercury lamps. In the case of black light, long-wave UV radiations are emitted by the lamp. Other artificial ways to produce UV light include the use of gas-discharge and short wave ultraviolet lamps, ultraviolet LEDs and lasers (NASA, 2013).
The UV light has a huge range of applications mainly due to its ability to initiate chemical reactions as well as the ability to excite fluorescence in a many materials. The use of UV light is mainly dependent on the wavelength band at which the light is transmitted. Different wavelength bands have different applications with the band ranging from 13.5 nm to 700 nm. Some of the applications include being used in lithography (13.5 nm), photoionization and photoelectron spectroscopy (30-200 nm), label tracking and barcodes (230-365 nm), water and surface decontamination, as well as disinfection (240-280 nm), and drug detection and forensic analysis (200-400 nm) (NASA, 2013).
Other applications include use in protein analysis, sequencing of DNA, use in drug discovery, and in imaging of cells in the medical field. In addition, UV light is also used in medicine for light therapy and in manufacturing industries in curing of printer inks and polymers. Other uses include hardening of different types of dental fillings, detection of fake bank notes and in getting sun tan. Since controlled UV doses triggers the body to produce vitamin D, UV light is used by doctors in the treatment of vitamin D deficiency, as well as other skin disorders (Darvill, 2012).
Darvill, A. (2012). Ultra Violet. Retrieved May 29, 2014, from http://www.darvill.clara.net/emag/emaguv.htm
Hockberger, P. E. (2002). A history of ultraviolet photobiology for humans, animals and microorganisms. Photochemistry and Photobiology, 76(6), 561–579.
NASA. (2013). Ultraviolet Light from our Sun. Retrieved May 29, 2014, from http://missionscience.nasa.gov/ems/10_ultravioletwaves.html