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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1answer
140 views

Red color has largest wavelenght and violet minimum (in the range of visible light). then why does violet light appears reddish? RED + BLUE = VIOLET [duplicate]

My question is simple. Green light is more similar to red light than violet, then why is violet reddish and green not? in the language of frequencies and wavelengths, red and violet should contrast ...
2
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1answer
97 views

Is there a one-to-one relationship between colour theories and our trichromatic vision?

This has started to bug me more and moreā€¦ it involves: colour theory the trichromatic properties of our eyes through cone cells and light. Is there a one-to-one relationship between colour ...
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2answers
455 views

Electron model under Maxwell's theory

I was not able to recall my memories, so: What is the formula that states the frequency of electrons revolving around nucleus is equal to the frequency of light (or photon) emitted (or radiated)? (I ...
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4answers
4k views

Why is there a difference between additive and subtractive trichromatic color theories?

Helmholtz distinguished between additive and subtractive trichromatic color theories. Additive theories concern optical combinations of colored light sources and are usually modelled on RGB while ...
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1answer
147 views

The range of light

It occurs to me that the empirical evidence shows that there is a point out in space where light stops coming from. Putting aside the expansion of the universe for a second, and focusing strictly on ...
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1answer
511 views

Snell's Law of Refraction

I was told that "Snell's law of refraction implies that a light ray in an isotropic medium travels from point a to point b in stationary time." Why is this true? Thanks.
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2answers
84 views

Does any material glow, under appropriate conditions?

Given a high enough temperature, or a high enough electrical field, can we make every material emit visible light?
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3answers
117 views

How far does a Photon's field Extend?

I read the related answer to whether photons have size, and the answer seemed to be it depends. If a Photon, or a rather an E&M wave has a magnetic and electric field, should things be able to ...
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2answers
365 views

Why are two independent sources incoherent?

Coherent sources are produced from a single parent source. But, why are two independent sources always incoherent? Two sources can produce light of the same frequency. Then, I guess the problem is ...
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0answers
85 views

How to get “massless” equation of motion from the action of Nordstrom scalar field theory?

There is Nordstrom theory of the particle moving in a scalar field $\varphi (x)$: $$ S = -m\int e^{\varphi (x)}\sqrt{\eta_{\alpha \beta}\frac{dx^{\alpha}}{d \lambda}\frac{dx^{\beta}}{d ...
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0answers
50 views

Is there any evidence that everyone sees colours the same way? [duplicate]

We all know that the sky is blue. Grass is green. Blood is red. But, how do we know that everyone sees these colours more or less the same? How does one know that my ...
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1answer
207 views

Principle of relativity and motion perpendicular to the direction of light beam

consider you are in a train that moves with a speed of $c/4$. A bulb is hanged from the ceiling. A light beam leaves the bulb downward. Exactly under the bulb on the floor is a detector. According to ...
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2answers
339 views

Is there a way to see light frequencies invisible to the human eye without the use of electronic sensors?

I wonder if it's possible to be able to see light frequencies that cannot be normally seen by human eye, without using sensors designed specifically for detecting a certain spectrum range, but rather ...
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1answer
3k views

Could the shadow move with faster-than-light speed? [duplicate]

If I make a huge laser with a figure for shadow in front of the laser, and I shine it on to the moon, will I see the light from the laser AND the shadow moving the same speed? (I read somewhere the ...
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2answers
2k views

Relativistic Doppler effect derivation

This is about a step in a derivation of the expression for the relativistic Doppler effect. Consider a source receding from an observer at a velocity $v$ along the line joining the two. Light is ...
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3answers
81 views

Trapping EM radiation [duplicate]

Is there a material which can allow light (or any other EM radiation) to pass through from one side as if it is transparent but its other side reflects light like a mirror?
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2answers
1k views

Reflectance vs. Thin Metal film Thickness Graph

Is there formula that gives reflectance of very thin film of given metal (tens of nanometers) to the visible light of given wavelength(808nm) ? Which properties of metals are needed for the formula ? ...
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1answer
338 views

How does a strobe lamp stop a fast moving object?

A strobe lamp can be used to seemingly stop a fast moving object when calibrated. Commonly used in quality assurance during production to inspect otherwise non-observable assembly line activity. What ...
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3answers
757 views

Conversion formula from spectrophotometer readings to any standard color space profile?

I have readings of colors from a spectrophotometer that records across the human visible color spectrum 390nm to 790nm intervals. I'd like to convert this into any color space, could be CIE XYZ, HSL, ...
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3answers
107 views

How to generate Red light from a Blue-Dominated Spectrum [closed]

I have a white LED light source, the spectrum of which looks as follows --- I want to filter out red light from this white LED source. But as you can see the spectrum dwindles in the red zone. And ...
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0answers
49 views

Mathematical formalism to include wave and particle perspectives of light

Does the exist any mathematical formalism (model) describing the behavior of light and incorporating its particle character (divisibility, quantization) and wave character? (i.e. quantized wave model) ...
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2answers
96 views

Observer looking out through the window of a train [duplicate]

When travelling by a train, it seems that the nearby objects move in the opposite direction(which I can explain) but the distant objects appear stationary. I can't explain this. By the concept of ...
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3answers
835 views

All objects radiate energy, but we cannot see all objects in the dark. Why?

We claim that all objects radiate energy by virtue of their temperature and yet we cannot see all objects in the dark. Why not?
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2answers
160 views

Does light have an unending journey?

When we shine a torch in a room its light travels to the back of the room. What happens to the light of a star ? I dont suppose we can say it continues to travel to the back of the universe as the ...
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0answers
117 views

Determining Ether Drag - Aberration of Starlight

In order to determine the relative motion between the Earth and the ether (the medium through which light supposedly propagated. It has zero density and complete transparency), scientists used the ...
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1answer
259 views

Transmission of Gaussian Beam Through Graded-Index Slab

The $ABCD$ matrix of a glass graded-index slab with refractive index $n(y)=n_0(1-\frac{1}{2}\alpha^{2}y^{2})$ and length $d$ is $A=\cos(\alpha d)$, $B=\frac{1}{\alpha}\sin(\alpha d)$, $C=-\alpha ...
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2answers
59 views

More about gravitation as the source of redshift of light beams [closed]

In the realm of physics there is no knowledge, the justification of which does not depend either upon experience or upon reason. In the light of the findings of the preconditions of knowledge made in ...
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5answers
294 views

Is velocity of light constant? [duplicate]

There is a difference between the concept of the speed of light and the velocity of light. are both of them constant ($dc=0$ and $dv_c=0$)? if yes, why?