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
553 views

Does a quadrupole transition mean emission of one photon with spin 2?

If it's true and spin-2 photons do exist, could you please point to some literature that discusses spin-2 photons? If not, then how exactly does a selection rule for quadrupole transition make sense ...
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3answers
465 views

Special Relativity - speed of light question

Just a basic question: I know that if you are traveling at $x$ speed the time will pass for you slower than to an observer that is relatively stopped. That's all just because a photon released at the ...
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2answers
395 views

Are there “gaps” in light, or will it hit everywhere?

Not sure how to word my question. Picture a light source in vacuum, so nothing disturbs the light (or similar conditions), 2d. If I move very, very far away, will it happen that some of the light ...
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1answer
169 views

william herschel discovering infrared problem

when william herschel conducted the experiment of separating white light with a prism and measuring the different colors, he put a thermometer past the red color as a control finding it to pick up the ...
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1answer
226 views

Which fraction of light is refracted from a source of light under a lake?

I was trying to solve this problem: "A punctiform source of light is standing inside a lake, at a height h of the surface. f is the fraction of the total of energy emitted that escapes directly from ...
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1answer
4k views

Magnifying Glass-How does it work? [duplicate]

How does a magnifying glass work? I know it creates a virtual image of the observed object but how is it possible that humans can see the virtual image?
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2answers
91 views

Hurdles in creating (close to) infinite images [duplicate]

Let's put an object (hypothetical superman) inside a "well sealed" box containing only mirrors. Is it possible to create number of images that will be close to infinity, assuming that resolution of ...
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5answers
17k views

Why frequency doesn't change during refraction?

When light goes through one medium to another it's velocity and wavelength changes. Why frequency doesn't change in this phenomenon?
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2answers
3k views

How photons represent colors that you see?

Right now, my understanding is that, a mixture of photons of many different frequencies is perceived as white by your eye. While no photons at all, is perceived as black. And photons with the blue ...
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2answers
230 views

What mechanisms allow conductors to be transparent?

An electric field in a conductor causes charges to redistribute so as to cancel out the original field, bringing the field to zero. This is, I think, a common argument for why conductors are generally ...
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5answers
3k views

Eye sensitivity & Danger signal

Why are danger signal in red, when the eye is most sensitive to yellow-green? You can check luminosity function for more details...
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1answer
201 views

Is a holographic recorder able to capture a large full color picture? [closed]

Is it practical to attempt to build a 3D hologram generator that is full color and big enough to recreate a watermelon full size? If so, is real-time control feasible?
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0answers
158 views

Are EM waves scattered the most when the wavelength and the obstacle have a similar size?

I heard that when the wavelength and obstacle are similar in size, the scattering is the greatest. Is this true?
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2answers
779 views

The color purple in a rainbow

In a rainbow the colors order is red then orange (made from red and yellow, thus making sense that it appears in between them) the yellow followed by green after which comes blue (again green formed ...
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3answers
250 views

If light is linearly polarized, does it have some spatial extent?

If light (a photon) is linearly polarized, say vertically, does it have some vertical spatial extent (perhaps in amplitude)?
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5answers
740 views

Will freely rotatable polarizers align?

Will two freely rotatable linear polarizers (placed in sequence and at some angular offset less than, say, 45 degrees) eventually align if you shine (plenty of) unpolarized light at the first one? If ...
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3answers
106 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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3answers
3k views

Light traveling through a medium

Does the frequency of light change when it travels across an interface between two media? What happens to the light wavelength and the light velocity at the interface? I've gotten different answers ...
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4answers
369 views

What does the wave principle of light actually represent?

Light has a dual nature, one of photons and the other of waves. But energy doesn't really travel in waves. So what do the wave represent?
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3answers
363 views

How does the solar sailing concept work?

Wikipedia describes solar sailing as a form of spacecraft propulsion using a combination of light and high speed ejected gasses from a star to push large ultra-thin mirrors to high speeds. I ...
2
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1answer
66 views

How does the Luminosity Function relate to the tristimulus sensitivity function?

In colorimetry, the irradiance spectrum is weighted with the luminosity function to obtain the perceived luminosity, and the tristimulus sensitivity functions to obtain the perceived ...
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1answer
77 views

choosing the right color

Context: My room is being painted, and i sit and study in a corner of the room, surrounded by walls on 2 sides, such that i am facing the wall. A tube light is at my 4-5 o'clock, and a ...
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0answers
148 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 ...
3
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2answers
143 views

Decomposing light into frequency spectrum

Light hits a charge coupled element. The wavelength of the light somehow is translated into a color picture. Where can I learn about methods (algorithms) to decompose light hitting a CCD into ...
2
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3answers
529 views

What starts the movement of a photon

Although a photon has no (rest) mass, it does have a measurable speed. Its movement can be altered by gravity. A photon "travels". If I turn on a flashlight, seen by someone at a distance, the photons ...
2
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1answer
203 views

Atomic physics through classical resonance?

I have a rather general question regarding the theory of Quantum Mechanics. To preface this question, consider a violin string. When a violinist exposes the string to a bow, this is exposing the ...
0
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1answer
179 views

Seeing a mirage through mirror?

Okay, I am not really good in physics (rather terrible), but nonetheless. So, I was just wondering if you can see a mirage, is there something special in our eyes that we can see it or what? I mean, ...
4
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1answer
439 views

Very large absorption lines in stellar spectrum

I was puzzled by the wide absorption lines in a stellar spectrum I found. The following is what I expect absorption lines to look like - thin, crisp lines: However, I found this stellar spectrum, ...
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3answers
191 views

How do we perceive colors outside our gamut?

Let's take an CIE XYZ color space as an example. There are many colors that are outside our gamut - how do we see such a color?
2
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1answer
650 views

Can an invisible light source cast shadows?

Let's assume that we have a mechanism for producing EM radiation suspended in the air, and that that mechanism itself is invisible to the naked eye (e.g. a microscopic light bulb on a microscopic wire ...
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2answers
1k views

Do photons actually generate a slight kinetic force?

My question is even though photons have no (rest) mass, do they emit a external force due to EM radiation causing electrons to be excited and jump to higher energy shells which electrons have mass ...
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2answers
98 views

Observing visible light itself by our eyes

We know that for any object to be seen by a human eye, the light from any source must be reflected from that object so that it reaches our eye and we can detect it.....but how do we see light itself? ...
17
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7answers
4k views

Why can't we store light in the form of light?

We can store cold (ice), heat (i.e. hot water bag) and electrical charge (batteries). We can even "store" a magnetic field in a magnet. We can convert light into energy and then, if we want, back to ...
4
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1answer
1k views

Gravitational Redshift around a Schwarzschild Black Hole

Let's say that I'm hovering in a rocket at constant spatial coordinates outside a Schwarzschild black hole. I drop a bulb into the black hole, and it emits some light at a distance of $r_e$ from the ...
0
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1answer
336 views

The nature of light

I'm not sure if this has been answered before, but I figured this would be the right forum to find out. I'm not by any means an expert in physics, just someone who's interested in understanding more ...
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1answer
554 views

How do photons experience time? [duplicate]

I know that as velocity approaches the speed of light the time dilation shoots to infinity as shown below. 1)So I want to know how time is perceived from the point of view of the photon? 2)Since ...
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3answers
1k views

EM waves: How do they travel for billions of km without damping

If a star is 1 billion light years away, it means that the light we see from the star is emmitted billions of years ago. How does this light not undergo a frequency change or get damped inspite of ...
3
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1answer
109 views

A question about how light hits a surface

my question is about how photons travel from a light source and hit an object. When you look at an object being hit by light the whole surface becomes brighter. What i'm trying to understand is why ...
0
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2answers
2k views

Young's Double Slit experiment question

Q-A beam of light consisting of two wavelenghts 600 nm and 450 nm is used to obtain interference in Young's Double Slit experiment (YDSE). Find the least distance from the central maximum where the ...
1
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0answers
26 views

Speed of Light in a Medium [duplicate]

For light travelling in a medium with refractive index greater than one: The "average" speed of light is slower than the speed of light in a vacuum. As far as I know, the instantaneous speed of light ...
2
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1answer
50 views

Is it possible to calculate chromacity coordinates using absorbance values?

I have absorbance values for blood plasma. Absorbance was measured in range of 380 – 600 nm every 5 nm ending up with absorbance values for 45 wave lengths. I was browsing through literature, and I ...
0
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1answer
357 views

What is the momentum of these emitted photons?

5 x 10^7 kg of radioactive material emits energy in the form of photons of red light (700 nm). (Note: photons have no mass.) What is the momentum of each photon? ...
12
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3answers
9k views

Is it possible to reproduce Double-slit experiment by myself at home?

I want to reproduce this experiment by myself. What I need for this. What parameters of slits and laser/another light source it needs? Is it possible to make DIY-detector?
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2answers
113 views

Can a stream of photons to be an environment for carrying light?

As the air molecules are environment for carrying sound waves, could stream of photons be environment for carrying electromagnetic waves? What contradictions cause this assumption in the existing ...
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2answers
2k views

Frequency Of Light

I am confused on few topics... What is meant by "Frequency of Light"? Does the Photon(s) vibrate, that is known as its frequency? If the Photons vibrate, then they have a specific frequency, then ...
9
votes
1answer
377 views

How fat is Feynman’s photon?

According to my calculations, it is a lot skinnier than Airy’s photon, but still a whole lot fatter than a straight line. So, how does a photon get from point A to Point B? The ray optics ...
5
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1answer
417 views

3D movie glasses making white light look red and blue

While waiting for a 3D movie to start, I was playing with the glasses they give you. I understand each lens has different polarized filters, so the left and right superimposed images on the screen go ...
0
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2answers
507 views

If we are travelling with the speed of light, can we see what's behind us? [closed]

If we are travelling with the speed of light, can we see whats behind us(like if we are moving away from earth can we able see the earth)? And how we see the things that we are approaching with speed ...
5
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3answers
180 views

How would I perceive a purple ball when traveling at relativistic speeds

I have a 'thought experiment' which I'd like to ask about. I was thinking what speed I would have to drive towards a crossing to see a red light as a green light - pretty easy, using the doppler ...
3
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3answers
261 views

Question on Radiance equation

The radiance equation is $$ L = \frac{d}{dA} \frac{2(\phi)}{dW cos(\theta)} (watt/srm^2) $$ where $\phi$ is the flux. I am thinking, should not be the cosine term on the numerator instead of the ...