Questions tagged [visible-light]

Questions related to the perception and measurement of light (primarily in the visible range), its mathematical description, the reproduction of colors by different means, color combinations, etc. Please use the tag [electromagnetic-radiation] if you want to refer to the general form of light.

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How to prove shadow blister effect is an eye trick?

I am trying to convince myself shadow blister effect is not due to diffraction, is there a way to test this? The wiki mentioned our brain is trying to fill in details when it can't exactly tell the ...
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What determine whether an object will absorb or transmit light?

If the energy of the light falling is not equal to the difference between any two orbitals of the atom then the electron absorb the light but re-emit it either through the object or reflect it ...
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How would you make a RGB LED equally bright to a broad-spectrum white LED?

Say you had a broad spectrum white LED (all visible wavelengths) and you wanted to make a RGB LED (just red-green-blue wavelengths) that could produce white light of equal brightness to the broad-spec ...
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Why visible light satisfies Maxwell equations? [duplicate]

As it is described in standard textbooks I looked at, the Maxwell equations were first established for electromagnetic fields created by electric currents. Then it is stated that it was discovered ...
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Can you create white light by combining cyan wavelengths (490-520nm) with red wavelengths (630-700nm)?

Cyan (blue light + green light) + red light = white light, but is the same true for cyan wavelengths ($490-520$ nm) and red wavelengths ($630-700$ nm)?
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Why does a gravitational field permanently alter the direction of photons?

Given we observe that light do follows path A (gravitational lensing) instead of path B, is there any direct empirical evidence about how photons and gravity interact, other than stating that photons ...
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Why is the brightest point of the shadow of a perfectly round object its middle?

What causes the Arago spot? Why does the line diffract like that? Wouldn't the light that diffracted and curved along the sphere go to as a straight line from its north or south pole? Why would it ...
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Why can we see light when it isn't being reflected back to us at the same angle?

If I am standing on a chair, and I point a laser at a coffee table a few meters away from me (that is also below me), the light should reflect away from me. Therefore, no light should be returning to ...
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Why is desaturated orange = brown, but desaturated blue is just plain blue? [duplicate]

As per wikipedia, "brown" refers to long wavelength hues, yellow, orange, or red, in combination with low luminance or saturation. So what about the short wavelength hues? Is there any ...
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Why is visible light right at the border of ionizing radiation?

I'm a physics layman, but was reading about ionizing vs. non-ionizing radiation, and it seems unlikely to be a coincidence that visible light (and some UV) spans the shortest wavelengths you can have ...
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Extrapolating Visible Sensor Data into the IR range

This question arises from an earlier Stack Overflow question on adapting raw camera data on an Android device for Infra Red, but was stumped on what Android Camera2 API makes available (https://...
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Where would reddish purples lie on the spectrum of light, considering red light and purple light are on opposite ends of the visible spectrum? [duplicate]

Obviously red and purple are opposite on the visible light spectrum. So how do we get colors that are reddish purple? Where would they lie on the spectrum of visible light?
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Colors: Lights Through Plastic

I have a blue plastic slide. On the outside of the slide, there are programmable led lights. If the lights are set to blue, I can see blue lights from the inside of the slide. If the lights are set to ...
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Is it possible to get a circle of colors from a CD on a wall with artificial light?

A CD acts as a diffraction grating and a circle of colors can be seen in a wall using the sun as a source of light. However I tried several types of lamps (incandescent, fluorescent and LED's) and ...
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Estimating dirt using total internal reflection :P

From total internal reflection experiments I came out with a question my professor couldn't answer me... is it possible to estimate the amount of particles in a surface from the change of the critical ...
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Cavitation plus sound equals light?

“If an underwater bubble is collapsed by loud sound, light is produced and no one knows why” says one of those click-bait social media posts with no citation—“light produced” and “no one knows why.” ...
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If the EM field weakens over distance, then why doesn't light weaken as it travels further from the source?

Just something I can't wrap my mind around. If light is oscillating EM field, and the strength of EM field weakens proportionally to distance squared, then why light doesn't lose energy as it travels ...
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How do you connect classical electromag, the photon, the wavefunction, and QFT to form a picture of light?

Classically, if you wiggle an electron in a sinusoidal pattern up and down, you get a smooth electromagnetic wave that propagates, kinda like when you wiggle a jump rope. Do this fast enough and you ...
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Inverting vision across $x$-axis? [closed]

Is there any type of lens or arrangement of lenses that would create an inversion of the $x$-axis of vision but not the $y$-axis? Preferably something that would be compact?
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Vision: eyes vs cameras

I think this is related to physics, and light waves. Is there some materials that can be seen by human eyes and can't be seen by cameras? (Imagine a special writing) Is that even possible therotically?...
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What exactly is a wave? What are waves, specifically light waves made of?

Do points in a wave move along with the wave? I was reading this post and I have become utterly confused with the concept of a wave. First, is a wave made up of particles or not? (Then again light is ...
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Light could travel around the closed FLRW universe precisely once?

I seem to remember reading somewhere that within the lifetime of a closed, recollapsing Friedman-Lemaitre-Robertson-Walker universe light could travel around the space precisely once. Could someone ...
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Clarifications about Lambert's law

I do not understand some things about the Lambert's emission law. Let's consider this text (reference): There is a common pattern to the angular distribution escaping light from certain diffuse ...
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When to rely on physical results derived using specific coordinates in GR?

I have been following a course on GR that at one point discusses the metric derived for the outside of a physical, non rotating uncharged massive object with spherical symmetry. For this situation I ...
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If at $t=0$, electromagnetic radiation was fed into the reflecting enclosure, how will the energy density within the Sphere change with time?

There is a Sphere which is $100\text{%}$ reflective by inside. And the radius of the sphere is increasing monotonically with time as $a(t)$. If at $t=0$, electromagnetic radiation was fed into the ...
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Why is light able to shine in a narrow beam?

If light is an electromagnetic wave how does light move in a line? Especially laser light. I thought that electromagnetic waves (as well as sound waves) can only expand in all directions as a sphere. ...
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Does light reflect from silver because of the difference in refractive index?

In a discussion with a friend, he seemed to be saying that reflection of light happens because of the difference in refractive index between two media, implying that that is the only reason reflection ...
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Why is the sky *uniformly* blue?

I've read a lot of answers to the questions why the sky is blue. However all the answers I found contain mostly qualitative analysis: Rayleigh scattering is changing the direction of blue light, so ...
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Formula for light attenuation

I was learning to simulate light in opengl and came across this formula for simulating light attenuation: $$F_{att} = \frac{1.0}{K_c+K_l d+K_qd^2}$$ where: $d$ represents the distance from the surface ...
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Book that deals with light attenuation

I was trying to learn derivations for formula of light's attenuation, and also from a book since background knowledge is usually given. Please recommend me some physics textbooks that deal with this. ...
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Monochromatic Polarization

What does it mean when we say that the monochromatic wave is un-polarized? Is this kind of wave actually possible? What would the equation of such a wave look like? Since we can consider also that ...
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Is speed of light in vacuum really constant? [closed]

According to sir maxwell the speed of light is constant irrespective of the observer. But according to sir newton anything in the universe is relative to something. If u say car is moving 10mph. Its ...
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Effect of black coating on the inside of a hobby telescope's hull?

I was watching this (rather old) episode of "The Making, where they show how a telescope is built in a factory. At 7:34, the cylindrical body of the telescope is shown to have a dark coating on ...
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Why do we subtract 90° from the incident angle when we want to find at which angle causes a refraction of 90° in a second medium?

As you can see we have 3 media here. Only focus on the glass and coating medium. Assume an incident ray comes from the air medium and is refracted inside the glass and then it is refracted again in ...
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How does Fermat's principle of least time for light apply to curved spacetime?

In a region of space which has no massive object light rays travel parallel to each other or ,simply, in a straight line. However, in a positively curved region of space (like near a planet or a star),...
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How could light beam keep its size with Huygens' principle?

In most of textbooks, the illustrations that being used to explain Huygens' principle are infinite wavefront or circular wavefront which works perfectly well to show how wave propagates. This ...
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In spectroscopy, what element does green indicate presence of in the atmosphere?

And what element does visible green glow indicate in our own atmosphere? https://youtu.be/HDlsdVuv6qQ
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Light and Photons Whole Numbered Frequencies [closed]

I was trying to make sense of color combining and prime colors. I was trying to look at it from an electron orbit and photon perspective. Aside from having an organ that over simplifies things, it ...
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Recomposed refracted light

could you say to me if white light in a prism with refraction => if we recompose the spectrum we will have white light again ? or what else ? since brown and magenta are not on the spectrum. What ...
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Why hyperbolic shapes of colour distortion in this image? [duplicate]

I took a photo of my computer screen through my mobile phone camera. Why are these color distortions in hyperbolic shape?
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How to explain interference of light by Huygens' principle? [duplicate]

there was an almost the same question here, but there was no appropriate answer(the answer there was incomplete and not to the point). now there is an updated answer to the question.
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Why does the moon sometimes look reddish yellow?

So the question is clear from the title itself. Only sometimes does the moon when it just rises above the horizon, looks reddish in colour. This mostly as I have seen occurs when the moon rises when ...
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Exceeding the speed of light by means of a shadow, will we ever be able to transmit information faster than light? [closed]

I bumped into this: Can a shadow move faster than the speed of light? while trying to see if I could find out anything about what I'd been thinking for 2 years now. Bear with me here, cause I'm only ...
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Why does fringe width in double slit experiment remain constant if slits get narrower?

The fringe width produced on a screen remains constant as the two double slits get narrower, but you are able to see more fringes on screen. I don't understand why the fringe width would remain at the ...
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Doubt in huygens principle

According to huygens principle, the light should move in every direction. But when I use a torch, it just goes in one direction. Why?
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Can I build a cuvette for 400-700 nm using simple microscope slides?

I want to measure the absorbance spectrum of some solutions, in the 400-700 nm range. I've always used regular "optical glass" cuvettes for this. But I've been wondering, is this really ...
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Does one observe light reach infinity in finite time in AdS spacetime?

I have a question about the following passage from this article: Moschidis imagined standing in the middle of AdS space-time, which would be like standing inside a giant ball whose edge or boundary ...
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If monochromatic light shines into our eyes, will that activate multiple types of cones or only one type of cone?

I have read this question: Explanation about black color, and hence color where John Rennie says: For example suppose you're looking at red light. Only the "red" cones will generate a signal and ...
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Are higher order interference peaks from a thin-film or multilayer of lower intensity, and if so why?

I seem to remember that higher orders (m) of interference for a thin-film (or multilayer) are increasingly weaker in intensity. That is, the first order interference will always produce a peak of the ...
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Why there are black holes that have a mass only 6 times the mass of the Sun?

We know that black holes are actually "black" because no light can escape them due to their gravity and that's why they appear black. That means the mass of the black hole most be extremely large even ...

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