Uv blue
On this Wikipedia the language links are at the top of the page across from the article title. UV radiation is also produced by uv blue arcs. Arc welders must wear eye protection and cover their skin to prevent photokeratitis and serious sunburn. Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact.
For humans, suntan and sunburn are familiar effects of exposure of the skin to UV light, along with an increased risk of skin cancer. The lower wavelength limit of human vision is conventionally taken as 400 nm, so ultraviolet rays are invisible to humans, although people can sometimes perceive light at shorter wavelengths than this. Ultraviolet rays are invisible to most humans. Humans also lack color receptor adaptations for ultraviolet rays. UV radiation was discovered in 1801 when the German physicist Johann Wilhelm Ritter observed that invisible rays just beyond the violet end of the visible spectrum darkened silver chloride-soaked paper more quickly than violet light itself. The discovery of the ultraviolet radiation with wavelengths below 200 nm, named “vacuum ultraviolet” because it is strongly absorbed by the oxygen in air, was made in 1893 by German physicist Victor Schumann.
Long-wave UV, black light, not absorbed by the ozone layer: soft UV. Short-wave UV, germicidal UV, ionizing radiation at shorter wavelengths, completely absorbed by the ozone layer and atmosphere: hard UV. Visible to birds, insects, and fish. 200 nm wavelengths can propagate through nitrogen.
Several solid-state and vacuum devices have been explored for use in different parts of the UV spectrum. Many approaches seek to adapt visible light-sensing devices, but these can suffer from unwanted response to visible light and various instabilities. Technology for VUV instrumentation was largely driven by solar astronomy for many decades. VUV radiation, and the development of solar-blind devices has been an important area of research. Wavelengths longer than about 30 nm interact mainly with the outer valence electrons of atoms, while wavelengths shorter than that interact mainly with inner-shell electrons and nuclei. Some sources use the distinction of “hard UV” and “soft UV”. The ozone layer then blocks most UVB.
Meanwhile, UVA is hardly affected by ozone, and most of it reaches the ground. UVA makes up almost all UV light that penetrates the Earth’s atmosphere. The Sun emits ultraviolet radiation at all wavelengths, including the extreme ultraviolet where it crosses into X-rays at 10 nm. The shorter bands of UVC, as well as even more-energetic UV radiation produced by the Sun, are absorbed by oxygen and generate the ozone in the ozone layer when single oxygen atoms produced by UV photolysis of dioxygen react with more dioxygen.
Suspended nanoparticles in stained-glass prevent UV rays from causing chemical reactions that change image colors. A set of stained-glass color-reference chips is planned to be used to calibrate the color cameras for the 2019 ESA Mars rover mission, since they will remain unfaded by the high level of UV present at the surface of Mars. World War I to block visible light for covert communications. Two black light fluorescent tubes, showing use.
BLB 18 inch, 15 watt tube, shown in the bottom image in a standard plug-in fluorescent fixture. BLB 12 inch, 8 watt tube, used in a portable battery-powered black light sold as a pet urine detector. A radiation and little visible light. A radiation instead of visible light. These are cheaper but very inefficient, emitting only a small fraction of a percent of their power as UV. B emitting bulbs are also sold for other special purposes, such as tanning lamps and reptile-husbandry. Black light’ incandescent lamps are also made from an incandescent light bulb with a filter coating which absorbs most visible light.
