What is Ultraviolet: Definition and 57 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. 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...
  2. B

    I "Packing of energy" question related to the ultraviolet catastrophe

    Hi, I'm curious about the ultraviolet catastrophe, and how Planck decided to hypothesize the quantization of energy integrally proportional to frequency to explain the drop off of energy in the higher frequencies. So what I don't understand is, when the energy is transmitted as a photon, does...
  3. Lotic7

    Geiger Counter and ultraviolet light sources

    I purchased a RadiationD-v1.1(Cajoe) geiger counter off ebay, and attached an arduino nano and a 16x2 display ( I got the instructions off this site https://www.instructables.com/id/Arduino-DIY-Geiger-Counter/). I noticed that the counter was sensitive to UV when I had it out in the sunlight, so...
  4. J

    B Ultraviolet Catastrophe & the Photoelectric Effect

    Hi, Please could somebody verify if what I have understood about the UV catastrophe is along the correct lines. I used this hyperphysics link: (http://hyperphysics.phy-astr.gsu.edu/hbase/mod6.html) Is it saying that using classical physics an object like a pen should be emitting just as much...
  5. Graeme M

    How does ultraviolet photography (fluorescence) work?

    I was reading my latest Reader's Digest in which appears an article about ultraviolet photography. The article explains that this kind of photography utilises a technique known as ultraviolet induced visible fluorescence. The article says that the technique allows flowers to reveal spectacular...
  6. R

    Relative eye safety of infrared and ultraviolet lasers

    My question is about the relative eye safety of infrared (##\lambda \gtrsim 1400 \ nm##) and ultraviolet (##\lambda \lesssim 300\ nm##) lasers. Both of these wavelengths are highly absorbed by the pre-retinal water content in the cornea, so they don't really penetrate into the retina. So one...
  7. 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...
  8. stoky

    Do car windows and windshields block ultraviolet light?

    I'm curious if car windshields / windows block UV (ultraviolet) light, the one from either the sun, or UV flashlights, like the Convoy S2+ Nichia 365nm.
  9. F

    Was the Ultraviolet Catastrophe a Real Problem or Just a Fake?

    Max Planck formulated the quantum hypothesis, that electromagnetic radiation was emitted from heated bodies only in quanta of energy E = hf, where f was the frequency of the radiation and h was a constant now called “Planck's Constant”, in order to solve the Ultraviolet Catastrophe...
  10. S

    Ultraviolet Laser Beam Shaping With Constraints

    Homework Statement Homework Equations Lens equation 1/f = 1/d_o + 1/d_i Minimum Gaussian beam spot 2*w_0 = ((4 * lamda * F)/(pi * D)) Where: w_0 = beam waist (half beam diameter) lambda = wavelength F = focal length of lens D = diameter of incoming spot Don't forget to match units. Let...
  11. P

    B Quantization of energy and ultraviolet catastrophe

    How can the quatization of energy solve the ultraviolet catastrophe? I tried explanation on internet and on the book but i found nothing, can you help me?
  12. 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??
  13. Asmaa Mohammad

    B What is the UV catastrophe and how does it challenge classical physics?

    when I read about the ultraviolet catastrophe on the internet I get a severe headache, and what I read in it doesn't stick in my mind, and my textbook says: "The classic physics failed in explaining the black body radiation because as a classical point of view the radiation is electromagnetic...
  14. Ez4u2cit

    Ultraviolet activated substances

    I recently purchased a bonding agent that is activated by an ultraviolet light (provided as part of the package). After three seconds of exposure to the UV light, the liquid substance turns rock hard. I believe they use the same process with modern dental fillings. Can anyone explain what is the...
  15. N

    How much energy can a plant absorb in ultraviolet light

    i want to know how much energy does a plant absorb in ultraviolet light, but i have no idea how i am going to do that.
  16. G

    Refractive index in the ultraviolet region

    When white light is refracted in a prism, we can see that blue color has the strongest refraction: the shorter the wavelength, the strongest the refraction. But the electromagnetic radiation with very short wavelength (X-rays) are not refracted by an amorphous solid such as glass: most part of...
  17. Alex299792458

    What absorbs Ultraviolet radiation?

    I know that ozone on Earth absorbs ultraviolet radiation but chemical or material absorbs ultraviolet light like the kind in fluorescent light that absorbs ultraviolet light and reemits it as visible light.
  18. Invutil

    Why is visible light not harmful?

    [unacceptable source deleted] Microwaves have a wavelength greater than visible light and are harmful. Ultraviolet light has wavelengths smaller than visible light and is harmful. In what ways are the two harmful and why isn't visible light harmful in the same ways? I'm a total noob. Just...
  19. G

    Why is it called the ultraviolet catastrophe?

    Why is it called the ultraviolet catastrophe rather than the visible catastrophe or the microwave catastrophe?
  20. gracy

    UV Radiation: Why Can't Human Eyes See It?

    why it is said that human eyes are unable to see ultraviolet radiation.sun emits ultraviolet radiation ,when we try to look at sun ,we see light coming from it (it is another thing that we can not resist that light longer and eyes shrink and we eventually have to stop doing so)but we do watch...
  21. J

    Can UV Light Be Converted into Visible Light?

    Hi everyone, Can anyone help me? Would it be possible to impregnate a transparent piece of plastic with compound which would shift incident UV light (preferably, from a variety of wavelengths of UV light) into light in the visible spectrum, whilst preserving the light's linearity? I have read...
  22. K

    Ultraviolet Catastrophe in simple language

    I am trying to understand what exactly the problem was that drove Plank to develop the quantum scale. I have read wiki about ultraviolet catastrophe and blackbody radiation, but I don't think I really understand what the problem was. Is sounds like the basic problem was that the wavelength of...
  23. C

    Reasoning in Deriving the Ultraviolet Catastrophe

    When one derives the ultraviolate catasrophe one looks at a cavity of perfectly conducting walls and with standing electromagnetic waves. Since these waves must vanish at the walls of the cavity, the wavelengths of the radiation is restricted according to the dimensions of the cavity: for...
  24. Absentee

    Understanding ultraviolet catastrophe

    Hey guys. I'm struggling to picture ultraviolet catastrophe. The graph tells me that at certain temperature, intensity should exponentially increase with decrease of wavelength. Of course, the theory is wrong, but how do i even PICTURE this with old model? If i imagine atoms in the dense...
  25. T

    Does thermal radiation involve ultraviolet x ray and jamma ray

    does thermal radiation involve ultraviolet x ray and jamma ray or just heat of light...
  26. K

    What is the blackbody problem and the ultraviolet catastrophe?

    Hello! I'm trying to research about the history and development of Quantum theory, especially with regards to Max Planck's energy quanta. I don't understand what was the problem in classical physics that required Planck to formulate quantum theory/energy quanta, which seemed to have...
  27. Artlav

    Filtering ultraviolet from Xenon arc lamp

    Hello. What sort of commonly accessible material can block harmful UV from a 150W Xenon arc lamp, without blocking much of visible light? Lamp relative spectrum (a bit around 250nm, growing to a lot at 400nm): Enough UV should be blocked for the lamp to be usable as a regular...
  28. C

    Difference in energy between visible line spectrum and ultraviolet?

    Homework Statement The emission spectrum of an unknown element contains two lines - one in the visible portion of the spectrum, and the other, ultraviolet. Based on the following figure and what you know about Niels Bohr's model of the atom, account for the difference in energy between these...
  29. Q

    Ultraviolet Catastrophe of Gravity

    Hi everyone! I was thinking about gravitational waves and gravitons and I realized that I did not fully understand the purpose of quantizing gravitational waves. I understand that quantizing electromagnetic waves gets rid of the classical physics prediction of the Ultraviolet Catastrophe (UVC)...
  30. J

    Blackbody radiation and the Ultraviolet Catastrophe

    Hi, please could someone help me as I am struggling to understand the classical blackbody theory. I will briefly summarize what my textbook says. It says that if the classical model was correct then a tennis ball should be emitting radiation in mainly the ultraviolet region. The idea at the time...
  31. S

    Do i have the ability to see in ultraviolet?

    ever since a few years ago when my and my sister both got black lights for our rooms [ i am myopic so i have to wear glasses] i have uv protection [non darkening] idk what it is but when i had my glasses on i saw the light a dark purple and the room would be darker and when i took my glasses...
  32. A

    Medical How can we protect ourselves from the harmful effects of UV rays?

    How can we safe us from ultraviolet rays? Guide me which diseases caused by ultraviolet rays?
  33. C

    What was the ultraviolet catastrophe

    I'm trying to get my head around exactly what this ultraviolet catastrophe is. So the early 20th century scientists were studying black body emission spectra (at constant temperatures) and plotted the intensity of the emitted light, against the frequency/wavelength. From what I've read...
  34. P

    Ultraviolet catastrophe and quantization

    Homework Statement I'm taking physical chemistry 2 right now and we are discussing the basics of quantum mechanics, and I'm trying to understand black body radiation and the ultraviolet catastrophe. What I don't understand is how quantization and Plancks distribution fix the ultraviolet...
  35. K

    Ultraviolet via dimensional regularization

    The integral: \intd^{3}k\frac{1}{k^{2}+m^{2}} is linearly divergent i.e. ultraviolet divergent. However, If one performs dimensional regularization to the above integral: \frac{1}{(2\pi)^d}\intd^{d}k\frac{1}{k^{2}+m^{2}}=\frac{(m^{2})^{d/2-1}}{(4\pi)^{d/2}}\Gamma(1-d/2) As you can notice...
  36. Q

    How does Quantum Physics solve the ultraviolet catastrophe?

    Hi, I understand how classical theory was wrong about blackbody radiation with the intensity reaching infinity as the frequency increased. However, I don't understand how the problem is solved with quantum physics. How does the fact that electromagnetic radiation be transferred as discrete...
  37. P

    Extreme Ultraviolet Wavelength Question

    On the Solar and Heliospheric Observatory (SOHO), a satellite which observes the sun from the First Lagrangian Point, there are 4 different Extreme Ultraviolet Imaging Telescopes, each with a different wavelength: 171 Angstrom - 1 million degrees Kelvin 195 Angstrom ~1.5 million degrees...
  38. F

    How Does Sunscreen Filter Out Ultraviolet Radiation?

    I am conducting a number of experiments for my Physics EEI, in which UV radiation levels are tested after passing through different types and thicknesses of sunscreens. From what I understand, the basic idea behind sunscreen is that some of the UV rays are reflected/scattered before reaching the...
  39. maverick_starstrider

    Why Do We Assume Ultraviolet Divergences are Physical

    Pardon me if this is a really silly question, my knowledge of field theory pretty much only comes from Condensed Matter. However, I know, before RG, QFT had a big problem with integrals blowing up unless you assume some cut-off frequency exists. My question is, what is WRONG with a cut-off...
  40. S

    Ultraviolet Curing to Make Metal Stronger

    hi, will putting titanium or carbon under ultraviolet light in a chamber make it much stronger, i seen a thing on 'nanotubes' but these are tiny pieces of tubular metal and they arent very usefull for my project, I am sure they was something simular to nanitubular technology but for lerger...
  41. J

    What exactly is the Ultraviolet Catastrophe?

    I tried looking it up, but I just don't get it. Something about intensity going to infinite(?) What exactly was the original theory and how does the "quantized" theory account for stuff? I'm sorry if this is a dumb question :/
  42. B

    What is Infared and Ultraviolet radiation responsible for?

    Please be as detailed as possibl. What do UV and Infared radiation affect, like how does infared energy have to do with heat?
  43. G

    Understanding the Ultraviolet Catastrophe: The Role of Planck's Quanta

    I'm just wondering what the specific problem and solution was for the ultraviolet catastrophe. I understand that it was because scientists were calculating that in an oven, the radiation was showing infinite energy. Is this due to their being an infinite number of waves or what? And whatever the...
  44. R

    Is Ultraviolet Light Really 'Beyond' Violet Light?

    Ultraviolet light question?? why is the term "ultraviolet light" misleading? is it because it is more on the violet end of the spectrum than violet light? any help please?
  45. S

    How does quantization of energy solve the ultraviolet catastrophe?

    Hi everybody, I have a question concerning uv catastrophe. I know light is quantized (photons) and I know the energy of a photon depends on the frequency (E=hv). However, I don't quite understand how this 'solves' the problem of uvc. I know the emission of light in a black body is due to...
  46. T

    What Are the Best Resources to Learn About UV Sanitization?

    I am a new product development engineer and am working on figuring out a UV sanitization product. Do you know of a good resource to understand UV rays, its properties, using UV, etc.? I am not looking for detailed math models and analysis, but rather, a resource that will help me...
  47. T

    Ultraviolet Rays - Need Resource

    I am a new product development engineer and am working on figuring out a UV sanitization product. Do you know of a good resource to understand UV rays, its properties, using UV, etc.? I am not looking for detailed math models and analysis, but rather, a resource that will help me...
  48. K

    Planck's law and ultraviolet catastrophe

    Hi. I know this is a pretty basic principle, however I'm fairly new to the subject and was wondering if anyone is able to give a brief 'layman' explanation of why, as Planck's law states, at lower wavelengths the blackbody radiation falls to zero rather than continuing to climb as stated in the...
  49. marcus

    Investigating the Ultraviolet Properties of Gravity with a Wilsonian RG Equation

    This paper may be slow to get the attention it merits because of its density and length. I have just printed out pages 1-5, and pages 64-70, from the introduction and conclusion sections, to chew over at leisure http://arxiv.org/abs/0805.2909 Investigating the Ultraviolet Properties of...
  50. K

    Why do we have to observe ultraviolet radiation using rockets or satellites?

    Why do we have to observe ultraviolet radiation using rockets or satellites, where as balloons are sufficient for obervations?