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.
0
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1answer
63 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 ...
0
votes
2answers
214 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?
0
votes
1answer
39 views
hurdles in creating (close to) infinite images
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 our ...
3
votes
3answers
230 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?
4
votes
2answers
182 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 ...
10
votes
2answers
113 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 ...
3
votes
4answers
233 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...
1
vote
1answer
141 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?
0
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0answers
60 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?
0
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1answer
75 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 ...
9
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1answer
101 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)?
8
votes
5answers
653 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 ...
1
vote
3answers
40 views
Trapping EM radiation
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?
1
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4answers
213 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
115 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
62 views
How is does the solar sailing concept work?
This wiki page states the following about solar sailing, "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 ...
2
votes
0answers
30 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 ...
0
votes
1answer
56 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 ...
0
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0answers
54 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 ...
2
votes
2answers
89 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
votes
3answers
137 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
votes
1answer
67 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
votes
1answer
75 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
votes
1answer
103 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, ...
0
votes
3answers
113 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
votes
1answer
131 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 ...
1
vote
2answers
103 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 ...
0
votes
2answers
62 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? ...
14
votes
6answers
1k views
Why cannot we store light in 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 magnete. We can convert light into energy and then, if we want, back to ...
2
votes
1answer
266 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
votes
1answer
103 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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votes
1answer
104 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 ...
0
votes
2answers
219 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 ...
2
votes
1answer
61 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
votes
2answers
236 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
vote
0answers
11 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 ...
1
vote
0answers
13 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
votes
1answer
66 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?
...
8
votes
3answers
710 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?
0
votes
2answers
54 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 ...
-1
votes
1answer
167 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 ...
0
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0answers
17 views
How wide is a pre- and post-selected light beam?
To pre-select the beam, we will require that it pass through two holes A and B.
This will allow us to select both a diameter and a divergence angle.
To post-select the beam, we will require that it ...
4
votes
0answers
122 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
votes
1answer
152 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 ...
-2
votes
2answers
106 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 ...
3
votes
1answer
78 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 ...
2
votes
1answer
78 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 ...
-1
votes
1answer
86 views
Are more/other colors posible with other dimensions?
Like these impossible colors (yellow/blue and green/red) or these imaginary colors, for example saturated red more intense than pure spectral red can be viewed in ordinary viewing conditions. Can ...
3
votes
1answer
122 views
Was the choice of red/green colors for traffic lights a happy coincidence?
All of us have learned since secondary school that the reason we use red in the traffic lights for "Stop" is because it travels the furthest without dispersion. According to wikipedia which cites ...
0
votes
1answer
54 views
Any suggestions for units conversion? [duplicate]
Possible Duplicate:
Photometer: measured Irradiance L converted to photon rate
I am conducting a experiment where stimulus output of $470\ nm$ is measured by a radiometer at $30\ \mu W\ ...
