Ultraviolet (UV) radiation is a form of non-ionizing radiation that is emitted from the sun and artificial sources, such as tanning beds. While it has some benefits for people, such as the creation of vitamin D, it can also cause health risks. UV radiation is found between visible light and X-rays along the electromagnetic spectrum, covering a range of wavelengths between approximately 10 and 400 nanometers. The wavelength of violet light is about 400 nanometers (or 4,000 AH), fluctuating at speeds between 800 terahertz (THz or 1012 hertz) and 30,000 THz.
UV radiation is similar to visible light in all physical aspects, except that it doesn't allow us to see things. The light that allows us to see things is called visible light and is made up of the colors we see in a rainbow. The ultraviolet region starts just after the violet end of the rainbow. Even though human eyes can't detect UV light, we can see its effects.
For example, even though the Earth's atmosphere filters much of the Sun's ultraviolet light, we may experience that it as a sunburn on our skin. The air can be treated by passing through a single UV source that operates at 184 nm and passing it through iron pentaoxide to remove the ozone produced by the UV lamp. UV detectors, which are sensitive to UV rays anywhere on the spectrum, respond to irradiation from sunlight and artificial light. The shorter bands of UVC rays, as well as the even more energetic UV radiation produced by the Sun, are absorbed by oxygen and generate ozone in the ozone layer when the individual oxygen atoms produced by the UV photolysis of dioxygen react with more dioxygen.
The purpose of melanin is to absorb UV radiation and to dissipate energy in the form of harmless heat, protecting the skin against direct and indirect DNA damage caused by UV rays. Electronic components that require clear transparency for light to enter or exit (photovoltaic panels and sensors) can be encapsulated with acrylic resins that cure with UV energy. The WHO standard ultraviolet index is a widely disseminated measure of the total intensity of UV wavelengths that cause sunburn on human skin, by which exposure to UV rays is evaluated based on the effects of the action spectrum at a given time and place. The image on the right shows three different galaxies taken in visible light (the three lower images) and in ultraviolet light (upper row) taken by NASA's Ultraviolet Imaging Telescope (UIT) on the Astro-2 mission.
Examples of eye disorders resulting from exposure to UV rays include sudden burns, frosted glass eyeball, welder glare, and blindness caused by snow, depending on the source of UV light causing the injury. Birds have a fourth color receiver for UV rays; this, together with eye structures that transmit more UV rays, provides smaller birds with real UV vision. Colorless fluorescent dyes, which emit blue light under UV rays, are added as optical brighteners to paper and fabrics. Some scientific instruments use halogen lamps with molten quartz envelopes as low-cost UV light sources in the range close to UV rays, 400 to 300 nm.
The COS and STIS break down the light of a single object into the colors that compose it, just as a prism divides white light into a rainbow, recording what is known as a spectrum. Knowing that the photographic paper would turn black more quickly with blue light than with red light, he exposed the paper to light beyond violet. UV fluorescent dyes that shine in primary colors are used in paints, papers, and textiles to improve color under daylight or to provide special effects when illuminated with UV lamps. Extreme UV radiation has the shortest wavelength range and the highest energies of the regions of the ultraviolet spectrum, and lies on the border between UV and X-ray radiation.
