uv light Definition and Topics - 11 Discussions

Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules.
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 amount of UV light produced by the Sun means that the Earth would not be able to sustain life on dry land if most of that light were not filtered out by the atmosphere. More energetic, shorter-wavelength "extreme" UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground. However, ultraviolet light (specifically, UVB) is also responsible for the formation of vitamin D in most land vertebrates, including humans. The UV spectrum, thus, has effects both beneficial and harmful to life.
The lower wavelength limit of human vision is conventionally taken as 400 nm, so ultraviolet rays are invisible to humans, although some people can perceive light at slightly shorter wavelengths than this. Insects, birds, and some mammals can see near-UV (i.e., slightly shorter wavelengths than what humans can see).

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  1. J

    Materials that allow IR or UV light to pass through?

    Glass allows visible light to pass through I would like to find a list of materials that allows lights of different EM spectrum to pass through, not just the above, Searched throughout google, couldn't find any!.
  2. SW Dad

    UV light + electric current = boom?

    Hi, so I was hoping to get an EE's explanation for what just happened. So my son was apparently over by the light switch pointing a UV pen light at the switch. Suddenly there was very loud, gunshot-like pop, sparks flew, and I had to go reset the breaker. Maybe correlation doesn't imply...
  3. D

    Best way to calculate UV-Vis absorption onset?

    Homework Statement Hello, I have a bunch of UV-Vis spectra to analyze and I am having a hard time choosing what the "onset" of each spectrum is, which I will use to calculate the optical band gap of each spectrum. Homework Equations The Attempt at a Solution I read somewhere that plotting...
  4. acvtre

    UV-vis amine problem

    Good day to everybody, I immediately expose my problem. I'm doing some measurements with the UV-vis spectroscopy and I'm having problems with the amines in the non visible region. This is what I do: put my amine in a quartz cuvette -> do the background (reference) -> analyze the same solution...
  5. C

    Help with uv light

    Hi everybody! I was hoping I could get some insight on how to calculate the energy of uva and uvb radiation at elevation levels of 0m in equatorial regions and at a lattitude of 35° N at 4500m in watts per square meter. Specifically, light in the range of 300-420nm. Any help would be...
  6. Garlic

    UV Lamp specifications

    Hello everyone, I own a handheld UV lamp, it looks like this: I've been using it for my hobby interests, like finding out what luminescent materials at home etc. Recently a friend of mine told me that germ killing uv light could be dangerous to sensitive retina parts. I know that this...
  7. Garlic

    Blocking violet light leakage in UV lights

    Hello, I have a handheld UV mercury vapor lamp, which, when working, leaks some visible light around violet wavelengths. My question is whether it is possible to block violet light but let the UV light using some kind of colored transparent sheets. Thank you..
  8. S

    UV Light Penetration

    For a photopolymer, the heuristic goes that longer wavelengths of UV light penetrate deeper than shorter wavelengths of UV light. For example, the UVA spectrum penetrates more deeply into the photopolymer than the UVC spectrum. What is the best way for this to be explained?
  9. S

    UV Light Penetration Depth

    For a photopolymer, the heuristic goes that longer wavelengths of UV light penetrate deeper than shorter wavelengths of UV light. For example, the UVA spectrum penetrates more deeply into the photopolymer than the UVC spectrum. What is the best way for this to be explained?
  10. Jesse44

    Black Lights and plain CFL and Cancer?

    Hello, so I have just learned that CFL bulbs fall in to the category of producing UV light, including perhaps some UVB in the case of black lights. I have had a black light bulb and a blue CFL running in my bedroom for almost two years now. I often fall asleep with the lights on, sometimes...
  11. M

    Excimer Structure

    Reposting from another section... Can anyone explain to me how an excimer is formed? Like structure wise? Considering Xenon. I've gathered that an excited state Xe*, ground state Xe, and a 3rd body M react resulting in an Xe* excimer + M(carrying away excess energy). I'm struggling to find...
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