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.
3
votes
2answers
270 views
Why does light of high frequency appear violet?
When people are asked to match monchromatic violet light with an additive mix of basic colours, they (paradoxically) mix in red. In fact, the CIE 1931 color space chromaticity diagram shows this ...
0
votes
2answers
37 views
Refraction of light and frequency dependence
Why do higher frequency waves refract more, both ocean waves and light waves? Also why is energy stored in the frequency as opposed to the wavelength.
2
votes
1answer
264 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 ...
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
vote
1answer
28 views
Relationship between photon polarization and photon angular momentum
What direction is the angular momentum of right hand polarized light points to? Is it vertical to its propagating direction? I want to recognize this in quantum theory.
0
votes
1answer
50 views
How to calculate beam spread of a non-point light source via an aspheric lens
I need to determine the angle, or rate of divergence of light from a single aspheric lens when I place a non-point light source (e.g. LED array) at a given distance from the lens which is less than ...
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 ...
-1
votes
1answer
161 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 ...
-1
votes
1answer
76 views
Are the speeds of the different wavelengths of visible light different or varying in a medium such as air?
Are the speeds of the different wavelengths of visible light different or varying in a medium such as air? If so, please inform by how much?
Also, even if the wavelength speeds vary minimally, please ...
4
votes
0answers
121 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 ...
3
votes
0answers
318 views
How to turn water opaque by pouring the smallest quantity of matter into it?
Consider a glass of water and a glass of coffee. Their contents differ by no more than a few grams of particles coming from the roasted and ground coffee, yet the former lets almost all visible light ...
2
votes
0answers
29 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 ...
2
votes
0answers
86 views
Bandgap Spacing in Photonic Crystals
I am doing some self-study on photonics and have encountered the following question:
We know that amorphous electronic crystals such as amorphous silicon have a bandgap. Can amorphous photonic ...
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 ...
1
vote
0answers
148 views
Splitting light into colors, mathematical expression (fourier transforms)
I am trying to solve a problem that includes a function of the light hitting a certain area. My question is, how would I change a function $G(x)$ of photons hitting a certain area to include just ...
1
vote
0answers
154 views
Representing a polarization vector for light as a 'manifold of two state'
Explain me these projections please
Context: I was reading a paper (Phys. Rev. A 68, 052307) which involved mesoscopic coherent states of light. There, in order to calculate the uncertainty of a ...
1
vote
0answers
31 views
What is the main downfall of using QPSK rather than DQPSK in fiber optics?
I've read that QPSK works theoretically in order to encode two bits depending on the phase of the signal. However, practically a reference for the carrier signal would be needed due to some ambiguity ...
1
vote
0answers
155 views
Does Infrared Light passes through Active Shutter Glass?
The glasses that we use for 3D viewing does it allow infrared rays to pass through them. Infrared rays pass through normal glass right? I need the pupil illuminated through infrared LEDs so I need to ...
1
vote
0answers
330 views
How to use the Coddington shape factor?
We are given $\sigma=\frac{r2+r1}{r2-r1}$, with $\sigma$ being the Coddington shape factor. What I am having problems with is solving for $r1$ and $r2$ when I am just given a focal length and a ...
1
vote
0answers
47 views
Light vs. X-ray interactions with Phosphor
Looking for some information on how light and xrays interact with phosphorous, or what might cause the following:
Scenario
A focus beam of light is directed at a phosphor plate at the same time as ...
0
votes
0answers
30 views
Historical aspect of wave theory of light
Huygens thought light as a wave. Wave is a propagation of physical disturbance. We now know that light is electromagnetic field. Electric and magnetic field fluctuates here. What Huygens really ...
0
votes
0answers
13 views
Minimum thickness of bubble ensuring max reflectance
A soap bubble has index of refraction of 1.33. What minimum thickness of this bubble will ensure max reflectance of normally incident 530 nm light?
Ans is 99.6, but how do I get that?
I am ...
0
votes
0answers
25 views
Interference of 2 slit experiment when glass is put infront of 1 slit (+0.5 lambda optical path)
The question and answer is given in the image below:
I don't really understand how to work this out myself. How do I relate $+\frac{1}{2} \lambda$ to (phase difference) $\Delta\Phi = \pi$
UPDATE
...
0
votes
0answers
59 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
votes
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 ...
0
votes
0answers
16 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 ...
0
votes
0answers
34 views
Need to write a function that computes the UV index
I have found a lot of people talking about how to compute the UV index, but have not found an example that shows the actual equations, so I could adapt them into an algorithm.
Probably the closest ...
0
votes
0answers
40 views
How does a lens affect the field of view in a mirror?
If one looks into a mirror, he can see a certain field of view.
If he places a convex lens that magnifies (or a concave lens that does the opposite) in front of the mirror, but so that he can still ...
0
votes
0answers
94 views
Why are subjects upside down when I look through my door peephole?
There is a convex lens 3/4" on the outside and 1 1/2" convex lens on the inside.
Each lens has one flat side facing out and one convex side facing in.
What can be done to correct this image?
0
votes
0answers
51 views
Image intensity when light is located in front of camera
According to papers, Image intensity has relationship with light intensity,
$L = ch(v)$
where $L$ is image intensity, $v$ is light intensity, $h$ is a nonlinear function $0<h(v)<1$ and c is ...
0
votes
0answers
191 views
Is Photosynthetic Photon Flux Density (PPFD) a synonym for Photosynthetically Active Radiation (PAR)?
Both have units of $\mu\text{mol m}^{-2}\text{s}^{-1}$ and refer to light in the 400-700 nm range - that activates photosynthesis. However, I just want to confirm that these are synonyms and don't ...
