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 much energy will fall into the eye given luminosity of display

The smart-glasses have tiny display. The manufacturer says the display has luminosity of $2000 cd/m^2$. The area of display is around $0.0002 m^2$. The reference smartphone display has luminosity of ...
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0answers
17 views

Transparency of atoms [duplicate]

Which is the specificity of the atoms which allow to pass the light, from which mass, from which composition of the core or the number of atoms the transparency falls. Electrons can collide with the ...
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2answers
58 views

Why conductors don't scatter light?

Air molecules can be oscillated by E field and re-radiate EM waves in different directions. However, if light is shined to a conductor the E field oscillate the free charges but the effect is to ...
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2answers
107 views

How do EM waves travel in a vacuum? [duplicate]

Apart from that electric and magnetic field variation thing, is there any other explanation? Can photons simply pass through vacuum?
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1answer
87 views

Why, in Chroma key composting, green colour is used? [closed]

In movie shootings, we observe that the Chroma Key Composting method is used very widely. Why do they only use dark green colour, what not some other like white, blue etc,
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1answer
44 views

If an atom emits a visible photon doesn't that mean it's visible?

A visible photon can be emitted and absorbed by an individual atom. Is this process sufficient for saying that we can see an individual atom with visible light? I realize the wavelength of visible ...
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0answers
26 views

Polarized light from any suface?

From a textbook I read something like this: "When sunlight is reflected from a horizontal surface, the plane of incidence is vertical, and the reflected light contains a preponderance of light that is ...
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2answers
119 views

How light splits up into different colours when passed through prism using QED?

I want to know how light gets splits up into different colours when it is passed through prism? How light interacts with atoms and electrons of the prism? Can someone explain this to me using Quantum ...
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0answers
252 views

Variable wavelength LED

Does there exist a type of LED (or other type of light source) that can change it's wavelength depending on the current/voltage it receives on a second wire? If not, would something like this even be ...
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1answer
118 views

Mechanism for visible light frequency mixing in storm clouds

So I know that when red and blue light (or the frequencies/wavelengths we percieve as such) hit our eyes with the correct proportions, our eyes and brains interpret that as the color purple. In ...
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0answers
19 views

Why does time stand still for light? [duplicate]

The source for this is the book "Einstein for Dummies", page 330, chapter 10.
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1answer
50 views

Light photon direction in movement

I recently watched a couple science videos on YouTube and left me with a doubt. If a spaceship goes to a really fast speed in the (horizontal) $x$-direction, what would happen if it shoots a light ...
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2answers
61 views

Does light ever experiences acceleration? [duplicate]

Till now I have learned that light has fastest speed. But I have also noticed that wherever it travels it only experiences retardation. So I wanted to know if light ever felt acceleration naturally in ...
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0answers
34 views

Viewing tube light through small cracks

This question appeared on a test: If you peer through very small cracks between your fringes at a tube light some distance away will you see interference patterns, Fresnel patterns or Fraunhofer ...
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1answer
656 views

What is the frequency of the color black?

Our eyes don't see light; they detect vibrations in the 400-800 THz range that we call color. Since our eyes can detect the color we call black, what is its frequency?
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2answers
1k views

Why is the index of refraction different for different wavelengths? [duplicate]

The index of refraction can be written as $$n=\frac{\lambda_v}{\lambda_m}$$ where $\lambda_v$ is the wavelength in a vacuum and $\lambda_m$ is the wavelength in the medium. I’ve been told that since ...
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1answer
45 views

Converting spectra to rgb colour

I am having trouble obtaining RGB colour values from the spectra of an object. I have the specific flux $F_\nu$ as a function of $\nu$ for each pixel of the image I'd like to make, but am unsure of ...
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1answer
70 views

Counting modes Rayleigh-Jeans

In the derivation of the Rayleigh-Jeans Law, we count the number of EM modes in a square cavity. After calculating the number of allowed modes due to boundary conditions, we multiply it by a factor of ...
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8answers
9k views

Why can't we see light travelling from point A to B?

Let's say we have a cloud of dust which is a lightyear across and someone shoots a beam of light from point A to B , why it is not possible for an observer far far away to see the light while it ...
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0answers
45 views

What will occur if you place two light-detecting lamps detector-end to lightbulb-end in a dark room?

It all started when my brother posed me the question of what would happen if you put a light-detecting lamp inside a spherical mirror. I reasoned that it would detect that all was dark and turn on, ...
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1answer
101 views

Optics phenomenon with my glasses?

When I look through my glasses toward the extreme left, a very odd and intriguing phenomenon occurs: The border of everything I see is lined with a hazy blue lining on the left and a hazy yellow ...
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1answer
692 views

Why do we see brown light?

While researching about lasers (it's my hobby), it suddenly hit me: there are lasers for every color of the visible spectrum, but there are no brown lasers. Brown isn't even on the rainbow. How is it ...
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1answer
43 views

Colour of ocean water

Why does ocean water seem blue colour in some regions while green in some regions while river of pond water is never blue in colour?
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4answers
245 views

What do light wave oscillations look like? [duplicate]

High school physics student here, so please bear with me for a moment. I know that light waves oscillate, but I don't know how. In textbooks and diagrams they're portrayed as wavy lines traveling ...
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1answer
18 views

White light polarization by ground\sky

Why does light from the sun gets a slight (horizontal) polarization after bouncing from the ground? And same question for light which is scattered from the sky. Thanks.
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3answers
202 views

Is it accurate that light loses energy in the absence of gravity and gains energy in its presence?

I just read an article about the supervoid they found and this is suggested. If so, then I am more and more fascinated with the ties between light and gravity. Let me emphasize, every article that I ...
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0answers
121 views

How do I translate from CIE xyY color space to combinations of monochromatic wavelengths

Let's say I have a chromaticity point, on the CIE xyY color space that falls within the real colors. (Like y:0.1, x:0.4 Y:1 -- magenta)[1] I also know that humans can perceive the same color, when ...
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0answers
31 views

mixing colour of light

I have seen blue and yellow colours mix to form a light green shade. How can we explain this phenomenon, both in case of light and physical substances like paint ?
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1answer
344 views

Are shadows cast on mirror surfaces?

While moving an object between a light source and a clean mirror surface, its shadow seems hardly visible (at least compared with a non reflecting surface). Is it correct that the shadow is not ...
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1answer
259 views

Inside a spherical mirror

imagine standing inside a sphere composed entirely of mirror surface; what does this look like? inside is lit by an invisible light source if each point encounters a reflection of itself, what is ...
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3answers
295 views

Is the event horizon of black holes visibly sharp, or blurry?

As you come in closer to a black hole, how do you see the event horizon? Is it always like a clear-cut surface? Or it only looks clear-cut from a distance, but as you come closer to the black hole, ...
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3answers
95 views

Is black a color? If so, does space have a color?

Suppose I stand in a room without windows or lights, but there is a radio playing. Then I won't see anything, but there is light! It just isn't visible. Is the room black? Now consider an object ...
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1answer
28 views

How safe are perfumes in different kinds of light?

Odd question that may seem out of place but I think it's appropriate here! Perfumes degrade based on: High temperatures High humidity (such as in a bathroom) UV exposure The last aspect is what ...
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1answer
125 views

Could a magnetic field repel electromagnetic waves?

If I understand magnetism correctly, then two magnetic fields with opposing directions would repel each other. Could this same affect happen to electromagnetic waves? And if so, could it be reproduced ...
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2answers
298 views

How we are able to see Jupiter?

As everybody knows Jupiter is made up of gases and these gases mainly contain hydrogen and helium. Since light passes through gases and does not reflect when shining on them, how we are able to see ...
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2answers
61 views

Why under red light the additive synthesis of primary colors gives white where one primary color is absent?

Under White Light Under Red Light For instance, red & green under red light gives white.
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1answer
41 views

Can we measure the height of clouds using the sunset?

I was watching the sun set in San Francisco. As the Earth turns away from the Sun the tallest buildings remain lit longest. Light bending in the atmosphere allows this to last a bit longer. So, what ...
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1answer
47 views

Would I be able to see light coming towards me before it got to me

If I were in space looking at a star that just started producing light that was two light years away. Would I be able to see the light coming towards me?
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1answer
63 views

Different colors and Metamerism

Given the following graphs: They describe the response for two different colors . In addition that both colors are metamerism. My question is why? how can I prove it? Thanks
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3answers
45 views

About light nature [closed]

I have some particular questions about the nature of light...cause all I know from all sources is that it is a wave and a particle and stuffs, but if light "COMES" from all directions, and is in every ...
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2answers
46 views

What causes red skies? [duplicate]

This morning, as I was walking to work, I noticed that the skies were different. It had a reddish tint. What causes this?
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2answers
71 views

Is it possible to reverse the polarity of already polarized light using passive materials?

For a gizmo idea that I have, I want to understand if it's possible to "reverse/turn" the polarity of light using passive, relatively thin and cheap films, similar to what we see in 3d glasses or TN ...
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1answer
657 views

What does a light wave look like (3d model)

What does a light wave look like? The only models I can seem to find online are 2D waves, they just look like sin() graphs. I have seen the models of the two components of "light waves" (electric ...
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1answer
58 views

What happens to light when the light source is spinning rapidly

In Einsteins analogy to demonstrate relativity, he asked that we envision two trains moving at different velocities, and then imagine a light shone from one train to the other. Do we know what impact ...
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0answers
53 views

How is it that light is reflected in this way in these photos?

I took 2 photos, in one there's a shutter and in the other there's the light that is reflected from the shutter to the ceiling. As you know and as you see from the first image, the shutter has ...
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2answers
345 views

Huygen's principle and why can't we see atoms with light

First of all, I'd like to discuss Huygen's principle. In order to explain waves diffraction, it says that every point in a wave front behaves as a source, so the next wave front is the sum of all ...
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0answers
47 views

Does Silver posses a color or Is it colorless reflection? [duplicate]

Why is silver said to have a color whereas water is not? Water is colorless because is allows penetration of light and doesn't reflect a colored wavelength, whereas Silver reflects light from its ...
3
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1answer
66 views

Why does roughened silver look gray while paper white?

Looking at reflectance spectrum of silver, given e.g. here, we can say that more than about $95\%$ of light is reflected by silver. Similarly for white notebook paper, the spectrum is given here, and ...
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2answers
199 views

How do you convert RGB lux into a singular value? [closed]

I'm trying to understand the output from an RGBW optical sensor. According to the specification for the sensor this outputs lux. I was hoping someone could explain how the 3 RGB lux values relate to ...
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1answer
95 views

What would the rainbow look like if we could see the full EM spectrum? [duplicate]

Would the rainbow look different if we could see the full EM spectrum (or at least a lot more of it)? Would the width of a rainbow be bigger and would all wave lengths of light be in a rainbow?