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 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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On Fig 4.1, draw the normal to the mirror at end P

I got given some homework to do over summer. It's a completely different exam board with a different specification. I understand it's hard to draw lines on this site but any help you could give me, ...
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3answers
49 views

What do light wave oscillations look like?

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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0answers
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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
72 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
42 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
24 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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2answers
649 views

Could an oscillator at a high enough frequency produce light instead of radio waves?

Considering that light is in the 400-800 THz range, if you had an electrical oscillator that ran at that frequency connected to an aerial of some sort, would the antenna emit visible light, in the ...
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11answers
18k views

Is it possible that there is a color our human eye can't see?

Is it possible that there's a color that our eye couldn't see? Like all of us are color blind to it. If there is, is it possible to detect/identify it?
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3answers
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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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1answer
130 views

Dispersion in a rectangular prism

Why are the colours visible only at the fringes of the light refracted through a rectangular prism?
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2answers
425 views

Finding the illuminance from a triangular light source

Since most light sources in games are point-like, it's pretty difficult to approximate area light sources with point sources. As triangles are a universal form to represent 3D models (thus area light ...
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6answers
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Very strange shadow phenomenon

I was laying on my bed, reading a book when the sun shone through the windows on my left. I happened to look at the wall on my right and noticed this very strange effect. The shadow of my elbow, when ...
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2answers
46 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
15 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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0answers
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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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2answers
203 views

Light wave crossing media and the relationship between speed, wavelength, and frequency

There are many threads on this topic (like this one) but one aspect about the equation $ v = \lambda\nu $ still confuses me. I have read that frequency does not change when light crosses into ...
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1answer
105 views

Path Difference Due to Angled Incident Light

If light incident on a diffraction grating makes an angle $\alpha$ with respect to the normal to the grating, show how $$m \lambda = d\sin\theta$$ becomes $$m\lambda = d[\sin(\theta - \alpha) + ...
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3answers
94 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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1answer
53 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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1answer
44 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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3answers
152 views

How is it possible for the wavelength of light to change in a medium?

So my physics class has just finished a long unit on optics while at the same time I've been trying to teach myself relativity. I admit my understanding is probably rudimentary, but I figured all the ...
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2answers
229 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
164 views

Explain the notion of light/electromagnetic waves/photons to a non-physicist

A non-physicist asked me about special relativity. My explanations naturally were based on gedankenexperiments involving light. This forced the question: "What is light? It is particles, isn't? Or is ...
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3answers
49 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
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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
53 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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1answer
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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? Update: How can I draw ...
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2answers
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1answer
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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
39 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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3answers
43 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
41 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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1answer
51 views

Why do we use Mie scattering to describe light scattering off large objects?

I'm an undergraduate student who has recently come across Rayleigh and Mie scattering and I'm trying to understand them a little better. As I understand it Rayligh scattering is used only when the ...
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4answers
83 views

Wall visible after light source removed

Let's say you have a lamp pointed at a wall, in a dark room with no other light source, if you turned off that lamp Would the wall still be visible for any amount of time?
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5answers
141 views

Why is microwave better than visible light for point to point data communication?

In the electromagnetic spectrum, it appears that the shorter the wave length, the better the bandwidth due to higher frequency. Some communication systems utilize microwave to transmit data to offer ...
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5answers
329 views

Can light travel slower than the maximum?

First of all, I know that light does indeed travel slower in a medium like air or water, but that's because the photons are bouncing off of the medium's particles and in different directions so the ...
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1answer
57 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
49 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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1answer
320 views

Can light exist without spacetime?

Since the medium in which light propagates is spacetime, would light be able to exist if spacetime did not exist? Is this like one of those chicken/egg problems, or can light be thought of as a ...
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1answer
240 views

Color of a Metal's Threshold Wavelength?

How do I find the color of the threshold wavelength if the metal has a threshold wavelength of $\mathrm{6.5\times 10^{-7}m}$? I know that converts down to $\mathrm{650\ nm}$, but can I still use the ...
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0answers
46 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
58 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
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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
41 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
1k views

Lux and W/m2 relationship?

I am reading a bit about solar energy, and for my own curiosity, I would really like to know the insolation on my balcony. That could tell me how much a solar panel could produce. Now, I don't have ...
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1answer
3k views

Refractive Index formula for denser to rarer medium

I learnt that the formula for refractive index when light travels from rarer to denser medium is $$\frac{\sin i }{ \sin r}$$ where $i =$ angle of incidence, $r =$ angle of refraction. Is the same ...
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2answers
40 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
34 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?
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1answer
33 views

Light / TEM wave in a hollow waveguide

I'm cramming for my EMF exam, and a question came up: Light in free space is an example for a TEM wave, isn't it? (Maybe thats already my mistake) And we learned that in a hollow waveguide only TE ...