Ultraviolet (UV), also part of the spectrum of the sun, plays an important role in our daily life. Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation is present in sunlight constituting about 10% of the total light output of the Sun. It is also produced by electric arcsand specialized lights, such as mercury-vapor lamps and UV LEDs. For the light spectrum of 315-400nm is the UV-A range, which is widely used in various industries. The applications of UV-A is to be discussed in this article.
UV-A lamp is widely used in MPI and FPI applications to excites fluorescent dyes settled on magnetic particles and resolved in penetrant to help locate surface cracks. The dyes are glowing in green, orange or red under UV-A, as shown below.
2. Leak testing
UV-A lamp is used for pipe or container leak testing. Fluorescent leak tracer is composed of carrier fluid (oil, solvent or water), additives and fluorescent dyes. During leak testing, leak tracer will be injected into close-circuit pipes or sealed containers. After a while, all connecting points will be checked under UV to detect leaking locations with fluorescence, as shown below.
3. Security and Forensics
UV is an investigative tool at the crime scene helpful in locating and identifying bodily fluids such as semen, blood, and saliva. For example, ejaculated fluids or saliva can be detected by high-power UV sources, irrespective of the structure or colour of the surface the fluid is deposited upon.UV-Vis microspectroscopy is also used to analyze trace evidence, such as textile fibers and paint chips, as well as questioned documents.
Urine under UV Finger print check under UV
Other applications include detecting counterfeit currency, credit cards and passports. The fluorescent marks on passports, cash, credit card and other IDs glow strongly under UV, which are invisible under white light.
Ultraviolet aids in the detection of organic material deposits that remain on surfaces where periodic cleaning and sanitizing may not have been properly accomplished. It is used in the hotel industry, manufacturing, and other industries where levels of cleanliness or contamination are inspected. Perennial news feature for many television news organizations involves an investigative reporter's using a similar device to reveal unsanitary conditions in hotels, public toilets, hand rails, and such.
UV curing is a process in which ultraviolet light and visible light is used to initiate a photochemical reaction that generates a crosslinked network of polymers. UV Curing is adaptable to printing, coating, decorating, stereolithography and assembling of a variety of products and materials owing to some of its key attributes, it is: a low temperature process, a high speed process, and a solventless process—cure is by polymerization rather than by evaporation.
6. Mineral & Gem Inspection
Ultraviolet lamps are widely used in analyzing minerals and gems. A collection of mineral samples brilliantly fluorescing at various wavelengths as shown below while being irradiated by UV light.
7. Agriculture & Pest Control
UV-A light is invisible to human beings, but visible to many insects. Some insects and living creatures are glowing under UV. UV attracts mosquito and is used to kill them with power grid, as shown below. Scorpions glows under UV-A (as shown below) and UV-A lamps are used to hunt scorpions during evening by pest control department.
8. Medical application
Many diseased skin and fungal infections show different colors under UV. The skin of a man with vitiligo has a strong contrast against normal skins under UV, as shown below.
9. Art examination and protection
In sum, UV-A light plays an important role in our life in the fields of photography, electrical and electronics industry, fluorescent dye uses, analytic uses, Material science uses and biology-related uses. It shows a different world from what we see everyday.
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