What is Uv: Definition and 185 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. A

    I What power rating do UV-A Tubes have? (tanning salons)

    good morning gentlemen I ask you a very simple question, do you remember solariums for tanning? they use tubes that emit uv rays A, what power (watts) does each single tube have? 10 Watts each?
  2. V

    Heat Radiation question (skin's reaction to UV versus IR radiation)

    I am not sure of the answer. But I am guessing that infra-red rays carry more heat radiation than ultra-violet rays, and the heat is instantly felt on our skin when exposed to both these rays. So what we feel is the heat sensation from infra-red rays and that sensation is missing when it's...
  3. C

    The derivative of uv wrt x using st function (homework problem)

    TL;DR Summary: I attempt to find the derivative of uv with respect to x using non standard analysis, hyperreals, and the standard part function st; I take u to be a function of x, and I also take v to be a function of x. Hello everyone! I've been learning about non standard analysis concepts...
  4. Lotto

    B What happens when ethane absorbs UV light?

    Because when I have two carbon atoms, they create a single bond, so their two electrons are in one boding orbital, but I have also one anti-bonding orbital here. And when the electron excitates from ##\sigma## to ##\sigma^*##, how can the bond between the carbon atoms exist? It has to disappear...
  5. A

    I Focusing UV light from a 275nm LED down to a small spot

    Hello, I'm trying to focus a 275nm (with proper safety precautions) LED that looks to be a few mm in length and width (the light-emitting portion) to a smaller dot size. The LED should probably be fairly close to the surface of the lens to collect more of the light. The dot size would hopefully...
  6. Buzz Bloom

    Medical An Odd Description of Skin Cancer Cause from UV Radiation

    Scientific American June 2, 2022 Vol 32 Number 6 Page 62 Title: Skin Cancer around the World Two Quotes: “The main cause of skin cancer is the exposure to the sun’s ultraviolet rays…” “UV radiation is about 40% stronger in New Zealand than it is at corresponding latitudes in the Northern...
  7. M

    Why aren't UV lasers being used in warfare?

    I've often seen it said that hobbyist-grade UV lasers, sold for a few hundred dollars to those brave enough to buy one, cause a serious risk of blindness. In the literature I see reference to eye damage from as little as 5 mJ/cm^2, which seems absurdly easy to attain. And every time I think of...
  8. D

    Optical Where to look for a UV light that is invisible to the naked eye?

    Where to look for a UV light that is invisible to the naked eye? Essentially I want to buy a UV light that doesn't have that annoying blue glow, I just want the UV light that is invisible to the naked eye like infrared light. I read a bit about it and from what I read what I'm looking for is...
  9. Furno

    B Is there a material that allows visible light and UV light to pass through?

    Is there a material that allows visible light and uv light to pass through? Edit: A physical material
  10. G

    Question UV plastic and rubber

    I have a PS2 Slim 90000 and its case is ABS plastic and it has rubber parts, this device is located on a wooden table, the lights with UV in my house and the sunlight coming into the house will dry out, crack and damage the ABS plastic and the rubber of this device? my house uses LED bulb
  11. N

    I UV mercury lamps: Changing the 185nm vs 253.7nm ratio

    According to Wikipedia, (citation needed) https://en.wikipedia.org/wiki/Ultraviolet What would alter this proportion of emitted radiation to favor more 185nm radiation? Preferably not with a filter that filters out 253.7nm (mathematically would also increase the ratio of radiance of...
  12. G

    Question about whether UV light can penetrate a cardboard box

    Does cardboard absorb or reflect UV from indirect sunlight? does it go through the cardboard and hit the plastic and rubber items inside the shoe box with UV?
  13. terminator 87

    Questions about UV light and dry plastic and rubber

    UV causes dryness of plastic and rubber and lights have UV so keeping it in the dark away from light inside boxes prevents this but notice this photo where the box where the arrows are marked the clarity q enters this region of the closed box is enough for the long term the UV of this clarity...
  14. S

    How to determine UV lamp dosage values of 10-20 mJ/cm2

    How do you compute whether a certain uv lamp can produce dosage values of say 10-20 mJ/cm2? Given the following lamp specs used in uv sterilizers. " TUV TL Mini UV-C Philips TUV 4W TUV TL Mini lamps are slim double-ended UVC (germicidal) lamps used in residential water and air disinfection...
  15. A

    Are Polycarbonate Sunglasses Effective Against UV Rays?

    Is sunglasses test with UV flashlight correct or not?
  16. jaumzaum

    A Why people say we can't "feel" UV?

    I was taught that the only radiation that we can properly "feel" is infrared, while UV is not properly absorbed by the molecules of our body in the form of thermal energy. But then I I saw the following picture which shows the water absorption spectrum: We can clearly see there that the UV...
  17. P

    Question about irradiance from a UV lamp

    Greetings all, I'm normally used to researching topics related to biology but I am currently tackling a related side project with UV irradiation, and I don't have much experience with radiometry. I have a compact UV lamp that I am using to irradiate a suspension of small particles (submicron...
  18. DariusP

    I Transmission and absorbance of materials in the deep UV

    I wanted to ask - why do some materials with very high transmittance inevitably start to absorb in deep UV? Is there an explanation?
  19. K

    UV degradation of different plastics?

    I have been searching on Google about UV degradation of plastics , polypropylene in particular. I understand fully that it will break the plastics and so many plastics / polypropylene are not suitable for usage under sunlight. I also found that on the molecular level the sunlight will break the...
  20. K

    A Exploring Rocket Exhaust Plume Molecules in the Upper Atmosphere

    I'm pondering the behavior and persistence of rocket exhaust plume molecules far above the atmosphere. For example, the plume from an apogee circularization thrust from GTO (Geosynchronous Transfer Orbit) to GEO (Geosynchronous orbit). CO₂ and H₂O are among the molecular species emitted by a...
  21. X

    B UV detection by fluorescent goggles

    I need to be able to detect and find shelter against the powerful UV radiation outdoors, since measuring devices are expensive and bulky, I decided to consider another method. Fluorescent materials are able to absorb UV light and re-emit as visible light. That gives me an idea to put fluorescent...
  22. A

    Light intensity at a distance -- UV light to kill bacteria

    I have obtained seeds of a rare rhododendron species. These seeds are contaminated (experimentally determined). While I have tried several common methods, none decontaminated the seeds. Lately, I have read that so many joules of UV light at approximately 254nm will prevent replication and...
  23. Zeynaz

    UV light and Fluorescent tubes

    I know that the answer is NO because now there is an extra substance (the fluorescent powder) that is affecting the emission. However, i don't know how fluorescent powder works in this case. I tried to search it up and only found that Fluorescent powder will 'fluoresce' when it absorbs UV...
  24. G

    I Why does a mercury Franck-Hertz tube produce visible light?

    Hi. I've recently conducted a Franck-Hertz experiment with mercury. I was able to see bluish glowing regions just as here: However, theory predicts 254 nm, which is far below visible. Are there other energy levels at play here? Wouldn't that mess up the 4.9-V-spaces of the drops in the current...
  25. M

    On Rayleigh Scattering and UV Light Absorption

    I've read that UV light cannot "penetrate" the atmosphere as easily during winter. But what does this exactly mean? My hypothesis is that due to rayleigh scattering, since light with smaller wave lengths scatter more, the UV light doesn't end up reaching the surface of the Earth (i.e. gets...
  26. G

    UV radiation vs. the real daytime exposure

    Hi, I have been solving one problem recently. I need to calculate, how many times faster is the aging under my UV lamp compared to the real sunlight exposure. I am pretty sure it will depend on the distance of the sample from the UV radiation source, it´s intense and exposure time. I would also...
  27. B

    Any bio-related benefit of UV radiation?

    We're all pretty familiar with the harmful effects of UV radiation on biological organisms, including us. My question is whether there is any necessary or beneficial effect of UV radiation. That is, if our atmosphere suddenly started blocking out 100% of UV while passing all other radiation as...
  28. S

    Optical filter that blocks infrared and allows UV?

    Hello. I want to build camera for ultraviolet photography and reflectography. I plan to use debayer'ed backlit CMOS camera with or without Wood's ZWB3 glass UV filter. But I also need to find infrared cut filter because abudant IR radiation will ruin photos. Problem is that there are plenty of...
  29. 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!.
  30. ADDA

    UV Map View Plane: Calculate 2D Position?

    Would there be a way to take a uv map and compute the 2 dimensional position of a viewing plane or eye or camera, without the need to expand the parametric equation into three dimensions? In the above video the uv map in the background yellow is calculated first. Then only the bright portions...
  31. B

    What Are the UV Radiation Risks of Using a Thyratron Tube?

    So I have an old RCA Thyatron tube (model 3C23) I'm using in an art piece as a glowing element. Just feeding maybe 50-60 watts through the anode to make it glow. My question is, do I have to be worried about UV radiation? I heard somewhere the glass was quartz or borosilicate and blocked it...
  32. 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...
  33. D

    Creating Coherent Light from UV LEDs and Pinhole Aperture

    I've read that using a pinhole aperture and a wavelength filter can turn a "white" incoherent light source like a light bulb into a temporally and spatially coherent light source (albeit at low efficiency). Can a temporally and spatially coherent light source be made with a monoenergetic (or...
  34. J

    Could UV lasers be used to split CO2 and H2O?

    I was wondering whether intense UV light, tuned to the correct wavelength, could be used to split carbon dioxide and water molecules as a first step towards synthesizing liquid fuels.
  35. S

    B Exploring the Origins of IR and UV in Particle Physics

    I assume UV means high energy (small scale) and IR is low energy (large scale).. but what is the exact origin of its use in particle physics? Why IR, UV, and not Gamma? Thank you.
  36. Fervent Freyja

    Are mosquitoes attracted by UV light?

    Are mosquitoes attracted to UV light? This PF thread isn't very clear on whether it does or not- some of it suggests that it does... So, I looked it up and found this article on Wikipedia: The American Mosquito Control association also http://www.mosquito.org/page/faq: Is the information...
  37. B

    Does a UV Lantern with Zapper Attract and Kill Mosquitoes Effectively?

    what kinds of flying insects can get attracted to the uv light in the lantern (sold everywhere) and get zapped? and what's the physics of how mosquitoes are attracted to them? is it because mosquitoes like the warm in the uv light and go there or their eye can see uv light and love to be in...
  38. L

    Ellipsometry- why is UV better than Visible light?

    Hello, I was wondering why UV ellipsometry is better than visible ellipsometry?
  39. ShayanJ

    A UV and IR modes in ground state

    I'm trying to understand chapter 19 of these lecture notes. But I have some difficulties with what the author explains: 1) In page 176, under equation 19.3 he says: This is weird. If we are considering a local QFT, then how can he say IR physics can cause non-locality? What is he talking...
  40. ORF

    I Why uranium glass glows green if it's under UV light?

    Hello Why the uranium glass glows green if it's under UV light? The most accurate thing I have found it's a brief history of uranium glass: somewhere it's said the more uranium oxide you put in the glass, the more intense will be the green light when exposed to UV light. Thank you for your...
  41. S

    A Effective field theories and UV completion

    In QCD, there are quarks at high energies, and pions are composite degrees of freedom that appear at low energy where the quarks are strongly coupled. The pion Lagrangian is non-renormalizable; it breaks down at the QCD scale and must be replaced by the full UV-complete theory of QCD...
  42. rodv92

    Decreasing gas breakdown distance in a spark gap with UV

    Hello ! I am currently investigating a technique that would allow several spark gaps to breakdown synchronously in an enclosed but not hermetical cavity, flushed with N2 at 1atm and ~25°C My idea was to use "indirect" photoionization (basically a synthetic fused quartz UV flash discharge inside...
  43. ReidMerrill

    Ligand Field Strength and UV absorbance

    I have a lab report for an experiment in which we used ion exchange chromatography to separate three Chromium complexes, CrCl2(OH2)4+, CrCl(OH2)52+, and Cr(OH2)63+ We used a UV vis to find the absorbance of each compound and used that to calculate the mole fraction of each ion in a mixture. One...
  44. Primroses

    IR divergences and UV divergences in perturbative QFT

    We know the following definitions in calculating amplitude (or a cross section) in momentum space: 1, Ultraviolet divergences are due to the infinity of the integration measure; 2, Infrared divergences are due to the singularity of the integrand; Now suppose we study a Feynman graph by...
  45. R

    B What else can UV rays be used for?

    **For example, drying a surface --> I know it has an effect on the skin, but if it were contained and blocked from sight, would it still leave any radiation emissions on any hard surface??
  46. B

    Amateur author seeking help on attacking ozone layer

    Hi, I'm looking for plausible fiction based content regarding environmental destruction. Sort of future UV wars or something. So here goes. Would appreciate any ideas or feedback on what I've come up with so far. Several dissidents build 12ft mirrored parabolic dishes which shine narrow focussed...
  47. N

    Can UV Light be the Key to Changing Venus' Atmosphere?

    I thought a bit about the prospect of terraforming other worlds starting with the ones closest to us, Mars and Venus. Personally even though I don't mind the hype over Mars, I prefer thinking of Venus as the main target for terraforming. it's just a lot more tempting. for example: It's surface...
  48. P

    Stop warping of photosensitive resin with desktop UV lamp

    Hey guys, Doing some research in medical physics and for testing purposes I am tryin to set SLA photosensitive resin with just a desktop lamp .. It sets fine but the problem is it warps and I'd like to set a thin sheet like 10cm square and about 1-2mm thick and keep it flat. Any brilliant ideas ?
  49. S

    B Are UV Films for Windows Really Effective in Blocking UV Rays?

    Hey everyone. Just a basic question out of curiosity. How effective are UV films for windows for blocking UV rays? Every window film I see says it blocks 99% of UV rays. I just put them in my house, and honestly, I find it hard to believe that it is blocking 99% of UV rays (that being rays from...