What is Visible light: Definition and 100 Discussions

Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). This wavelength means a frequency range of roughly 430–750 terahertz (THz).

The primary properties of visible light are intensity, propagation-direction, frequency or wavelength spectrum and polarization. Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature, as with all types of electromagnetic radiation (EMR), light is found in experimental conditions to always move at this speed in a vacuum.In physics, the term 'light' sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. Like all types of electromagnetic radiation, visible light propagates as waves. However, the energy imparted by the waves is absorbed at single locations the way particles are absorbed. The absorbed energy of the electromagnetic waves is called a photon and represents the quanta of light. When a wave of light is transformed and absorbed as a photon, the energy of the wave instantly collapses to a single location and this location is where the photon "arrives". This is what is called the wave function collapse. This dual wave-like and particle-like nature of light is known as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.
The main source of light on Earth is the Sun. Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps. With the development of electric lights and power systems, electric lighting has effectively replaced firelight.

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  1. aaaaautumn

    A Visualising visible light Fluorescence

    Hi all, I am new to physics forum and would appreciate all your input in this topic. I am trying to understand if an object fluoresces under UV light it is possible it may also Fluoresce under visible light? additionally would it be possible using band-pass filters (device that passes...
  2. B

    B Visible Light Through a Wormhole

    In the Stephen Baxter novel "The Light of Other Days," scientists develop a technology which allows information to be sent and received through a wormhole, first gamma-ray bursts then visible light. This technology develops into a near-omniscient camera system which allows a viewer to observe...
  3. B

    I Absorption cross section of light in air

    When I woke up today in the morning, I had the stupid idea of trying to remember some of my knowledge from university. As it turned out, this was easier thought than done, especially given my still drowsy state of mind. I want to roughly estimate the penetration depth of visible light in air...
  4. A

    I Can visible light cause fluorescence in colorful objects?

    https://en.wikipedia.org/wiki/Fluorescence You normally heard of Fluorescence coming from UV which make the objects glow. But visible light can also cause fluorescence. When you hit a colorful sample with a 532nm laser, there is fluorescence in the visible spectrum (as seen in Raman...
  5. F

    Finding Total Number of Optical Field Modes for Visible Light

    ρ_kdk = k^2/π^2 dk is the density of field modes (what we are trying to solve for here), and as ρ_kdk = ρ_λdλ, and k=2π/λ, we can rearrange this to get ρ_λdλ = 8π/λ^4dλ This is where my confusion lies. I am not sure what to do next. I know this equation physically means the number of modes per...
  6. 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
  7. K

    Calculating the degree of polarization of reflecting light

    I am looking for in an equation that's spits out the degree of polarization of reflected light, with incidence angle and the refractive indexes as inputs. an article online article had this graph decribing the degree of polarization as a value between 0 and 1 plotted against the angle of...
  8. Z

    Animals Beyond Visible Light & Infrared

    Do any animals see in a spectrum other than visible light and infrared?
  9. bhobba

    Exploring the Evidence for Visible Light as EM Radiation

    Hi All In discussing another issue it occurred to me the only experiential evidence I know that normal visible light is EM radiation is Faraday Rotation. I strongly suspect we have a lot more these days. Amusing story. Fermi's wife had a degree in general science that did not cover...
  10. nightvidcole

    Is Visible Light Bremsstrahlung Observable in Transparent Mediums?

    Summary: Can one observe visible light bremsstrahlung when an electron beam stops in a transparent medium? The theoretical form of a bremsstrahlung spectrum is flat at low photon energies. This means that even a high energy electron beam incident on matter should cause the emission of visible...
  11. R

    B Can photons of visible light lose energy and become sub-visible?

    Let me clarify this by a thought experiment: Imagine, a heated, red-hot (emitting only monochromatic red light) metal bar is brought inside a dark room. The room is practically insulated and the metal bar is glowing in the dark - emitting 'red photons' of visible light. Eventually, the bar...
  12. 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...
  13. sherzadakhan

    Visible light communication modulation schemes?

    visible light contains a range of frequencies i.e not of single frequency, then how visible light is used as a carrier in Visible light communication. Further more is it possible to modulate light (in tera HZ frequency range). what modulation scheme is possible and how it is implemented in VLC...
  14. A

    Optics: How would you determine wavelength?

    If there is an light source that is emitting light with the wl of 450nm (blue) and it illuminated a low reflective red object. How would the wavelength be different then if the object was a white object or the emitted light is from a white led. How would we determine this. I am working on a...
  15. R

    Refractive index as a function of the concentration of a sugar solution

    We recently performed an experiment with the idea to find refractive index of medium (water) as a function of wavelength of light. We then added some sugar to see how the refractive index changes with concentration of sugar solution. We got the following graphs. Are the relationships actually...
  16. R

    Visible light and light are two different things?

    Is this correct? Visible light refers to the visible light section of the spectrum and light generally means the rest of the spectrum?
  17. L

    Ellipsometry- why is UV better than Visible light?

    Hello, I was wondering why UV ellipsometry is better than visible ellipsometry?
  18. Anindya Mondal

    Why we don't use visible light to cook food?

    As we know that microwaves have less energy than visible light , then do we use microwave oven in cooking food instead of visible light?
  19. clamatoman

    Diffraction Grating - all visible light?

    Homework Statement Find the smallest grating spacing that let's you see the entire visible spectrum. 400nm to 700nm comprises the visible light spectrum. no other information is given. Homework Equations nλ=d sin θ The Attempt at a Solution I am not sure how to start as all i have been given...
  20. KennedYeti

    Diffraction Grating and Visible Light

    Homework Statement "You're using a diffraction grating o view the 400 to 700 nm visible spectrum. Suppose you can see the spectrum through the third order. a) Show that the first and second order spectra never overlap regardless of grating spacing. b) show that the second and third order...
  21. Clara Chung

    How does a gamma ray get converted to visible light

    In the process of heat transfer from core to photosphere, each gamma ray in the Sun's core is converted during scattering into several million visible light photons before escaping into space.----from Wikipedia How does heat transfer related to scattering? Is it related to Raman scattering as...
  22. C

    I Visible light reflection v.s X-Ray reflection

    I'm a bit new to studying physics so I hope this question doesn't sound off. I already know this "Photons are emitted from an atom when an electron transitions from one state to a lower-energy state. The energy of the emitted photon equal to the difference in energy between the two states."...
  23. adamaero

    Finding wavelength of visible light in a well

    Homework Statement Determine what colors of visible light would be absorbed by electrons in an infinite well, N = 3.1 nm. The effective mass for an electron is one-fifteenth of the standard electron mass. Homework Equations En = n2h2/(8mL2) E = hf f = c/λ The Attempt at a Solution E1 =...
  24. EngPhy

    A Effect of visible light on conductivity

    Are metals better conductors in the presence of visible light? Considering photons in visible spectrum are not energetic enough to induce emission from a metal surface but they do cause the ejection of 'conduction electrons' which are bound to the metal by a few electron volts.
  25. Frozen

    Seeing more than the visible light spectrum

    Maybe this sounds mad, but does anyone think it would be possible to see wavelengths that are beyond visible light, maybe through genetic engineering or through other technology? There are many animals than can see infrared & UV. Wouldn't it be cool if we could see what radio waves look like?
  26. M

    Work function of cathode, visible light

    Homework Statement You need to design a photodetector that can respond to the entire range of visible light (400 nm - 700 nm). What is the maximum possible work function? Homework Equations E = hf = hc/lambda The Attempt at a Solution For 400nm, I got E = 3.11 eV and for 700nm I got 1.78 eV...
  27. A

    Connect two objects with visible light

    Hey! I play cricket as a hobby, we have to mark the boundary. And we use cones to mark it(http://www.rkme.com/wp-content/uploads/product/cricket/CPR-08.jpg) Having it in limited number results in confrontation whether it is out of boundary or not. I am looking for solution for you guys...
  28. H

    Is Pluto's Visible Light Intensity Equal to Earth's?

    Is the visible light on the surface of Pluto equivalent in intensity to what it is on Earth? That is, is 1 lux = 1 lux even though it takes light that much longer to get there from the sun? Or are images of distant objects in the solar system taken with longer exposures?
  29. 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...
  30. E

    How would you convert visible light to infrared or microwave

    Is it possible to convert light in the visible spectrum to infrared or microwave light. What processes would be used to do this? Thanks, EJ
  31. R

    Material opaque to IR but transparent to visible light

    Hi all, I want to get some sort of polymer that is opaque to infrared (absorbs wavelengths above 700 nm very well) but transparent to visible light (does not absorb much light below 700 nm). Does this even exist without being a meta material?
  32. Timelord88

    How did "Visible light" come into existence?

    As i read when the big Bang happened,it was in a hot dense state for the first million years. Then the gases started to collect together and cool down,to form stars. (Sorry if i`m being wrong). So when did and how did the first ray of visible light came into existence?
  33. RAHIL008

    Why Is Binary Modulation Preferred in Visible Light Communication?

    I read that for VLC, they use toggling the LEDs ON/OFF to represent binaries. Why cannot we modulate the visible light like radio waves.
  34. gracy

    Understanding Benzene: Visible Light and Excited Electrons

    know benzene is colourless...but i can't seem to get my head around it at the moment! As benzene has delocalised electrons, it should require less energy to excite the electrons. And Visible light is a lower frequency to UV? So according to the equation: E=hv Benzene should be coloured as it...
  35. J

    The masking effect of the sky scattering of visible light

    It is very well known that the sky scattering of visible light decrease with the wavelength, it is bigger in the blue portion of the spectrum( the reason why the sky is blue ) and is lower on the red portion of the spectrum, this scattering is even lower on the infrared section and lower still...
  36. M

    Microwave Vs. Visible light Heating

    People always tell me that microwave ovens heat food by exciting the water molecules in food. This is done by blasting food with 2.4 Ghz radiation, the people that say this, also say that the frequency that is used is critical because that frequency interacts with the water molecules. I wonder...
  37. Feodalherren

    Solving for Visible Light Reflection/Transmission: A Homework Help Guide

    Homework Statement An oil film (n = 1.45) floating on water is illuminated by white light at normal incidence. The film is 280 nm thick. Find (a) the color of the light in the visible spectrum most strongly reflected and (b) the color of the light in the spectrum most strongly transmitted...
  38. A

    Can we produce a white laser from a visible light spectrum?

    I am doing a final year project, my Prof gave me 2 prism. He wants me to do so: A white laser is shot on a prism producing a visible light spectrum, use another prism to converge the spectrum back into a laser. For me, it is theoretically impossible and I tried to convince him that it...
  39. N

    Hydrogen Gas Transparency With Visible Light

    I'm reading my physics text, Matters and Interactions, and there is an example about why Hydrogen gas is transparent in visible light. It says it is transparent because visible light has energies from 1.8 to 3.1eV, and in order to move a Hydrogen atom from ground state to the first excited...
  40. K

    ?Radio Waves vs Visible Light: Is it Correct?

    radio waves propagate through air or penetrate material more than visible light. is it correct? why
  41. L

    Do the quantum effects we observe in visible light occur in all wave

    Hello everyone, I'd like to start off by expressing my appreciation for the existence of this forum to begin with. I majored in Sociology, yet classical and quantum physics has grasped my attention to a whole new level. Basically, I have a very elementary understanding in the subject, which is...
  42. T

    Does visible light contain energy?

    I read that Infra red waves that are absorbed are emitted by objects. And that makes sense. But then I read that it apparently works differently in the visible light spectrum, i.e. the visible light colors we see are only those that that aren’t absorbed, i.e. they’re only the ones that are...
  43. J

    Create visible light with spinning magnet?

    Let's say you have a strong spherical neodymium magnet (for the purposes of this example, let's give it a 1 cm diameter), and you were to place it on a machine which rapidly rotates the magnet. If you were to rotate it at 100 MHz, could you build an FM radio transmitter? Supposing it were...
  44. K

    Exploring Visible Light: Reflection & Energy

    how does visible light carry with it? does this energy increases with increase in number of reflection?
  45. W

    Can Visible Light Produce Heat When Absorbed?

    "dark materials absorb more thermal energy than lighter colored materials" Initially I thought this statement was very straight forward and obvious... then someone mentioned that visible light photons do not produce heat when absorbed and that IR was the only component that would be...
  46. iVenky

    Why can't we see objects smaller than wavelength of visible light?

    I read in Feynman's book that it is not possible to see objects less that wavelength of visible light with a microscope. That's the reason why we go for electron microscope. Why can't we objects which is less than wavelength of the information carrying medium (which in this case is visible light)?
  47. N

    Intro chem help Visible light spectrum? and energy of photon? help

    on a visible spectrum scale what are the numbers for the colors of ROYGBIV? for example is violet 400-500nm and red is 700-800nm? how about the other colors? If the energy of a photon is 2.63 x 10^-19 J, how can we tell what color this is? i was looking at this electromagnetic spectrum and it...
  48. R

    Determining the penetration levels of visible light

    Is there research or data that measures the penetration of various visible light colors on the human body?
  49. Q

    Detecting visible light EM radiation with an antenna

    If visible light is part of the EM spectrum just like radio waves, is it possible to construct a radio like antenna (metal pronged structure) to detect them?
  50. H

    Visible light wavelength discrepancy on the EM spectrum?

    Hello all, I'm not all too familiar with the electromagnetic spectrum, nor generally with physics but there is something that keeps me up. I learned, and also read now everywhere that visible light (to humans) lies in the wavelength range of about 400-700 nm. No I have a science book here...