All Questions
Tagged with optics visible-light
206
questions with no upvoted or accepted answers
7
votes
1
answer
152
views
How can daylight have a higher colour temperature (e.g. 6500 K or D65) than sunlight in space?
Supposedly, daylight at midday has a colour temperature of 6500 K. This reference is also the standard for calibrating computer screens (that's how I fell into this). However, outside the atmosphere ...
5
votes
3
answers
1k
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 ...
4
votes
1
answer
197
views
While flying over Rome we noticed that during sunset, there was a green color between the red and blue of the sunset sky. What causes it?
The picture has only been trimmed and not edited. The green is visible when the red or orange tapers off into the blue. Is this different from what causes the green flash? We were flying from Rome.
- 41
4
votes
1
answer
105
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Different Color Intenensities from simple ON/OFF RGB subpixels
I recently got interested in electronic paper.
One design that I liked was the one from Mirasol:
https://en.wikipedia.org/wiki/Interferometric_modulator_display
However, what I don't understand, is ...
- 829
4
votes
1
answer
2k
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Why does Light change color through Glass slab?
I shone a green laser light(~532 nm) through a glass slab and what I saw inside was that the light beam was now red.
Imagine a regular refraction diagram but color the beam outside green and that on ...
- 199
4
votes
0
answers
349
views
Optical Bloch oscillation
I have a doubt about how the optical Bloch oscillations happen in a 1D photonic crystal. I try to explain: in a photonic crystal with discrete translational symmetry in one direction I superimpose a ...
- 41
3
votes
0
answers
61
views
Why is sunset in mars blue?
This is the Martian sunset, as captured by the Spirit rover of NASA. Notice the colors are inverted, i.e. the direct rays blue and diffused rays red, which is exactly the opposite of what you would ...
- 12.5k
3
votes
0
answers
101
views
What creates the orange hue when there is wildfire smoke?
I find a variety of opposing arguments on the internet:
That this is due to Rayleigh scattering, which "removes" the blue light from reaching our eyes. This is similar to how the sunset ...
- 131
3
votes
0
answers
68
views
Do laser filaments propagate in a straight line over long distances?
In so-called filament propagation, a powerful laser beam can propagate through a medium without diffraction. This occurs because the beam focuses itself through non-linear optical effects. Self-...
- 4,080
3
votes
2
answers
84
views
What kind of light coherence is required for an image
If
1- Optically speaking, an image point (or pixel) is a light interference pattern
2- interference patterns require phase coherence
then
3- the source of the image point must emit coherent light
...
- 1,586
3
votes
1
answer
118
views
Why are powdered silver and powdered platinum black?
The quantum-mechanical (relativistic) explanations for the observed colours of copper, silver & gold don't appear to explain the black colours of powdered silver (& powdered platinum). Can ...
- 207
3
votes
0
answers
465
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Is there a wavelength of electromagnetic radiation that can penetrate iron but reflect off iron oxides?
We can see corrosion or rust because visible light travels through air reflects off the material back through the air and into our eyes. But I am wondering if you could see the corrosion through on ...
3
votes
0
answers
338
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 ...
- 283
3
votes
1
answer
206
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Why is refractive index equals to speed of light upon phase velocity and not group velocity?
We have been using group velocity for most purposes as its the velocity with which the wave packet travels, they why do we use phase velocity for calculating refractive index.
2
votes
2
answers
75
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If a weak light source is attached to a string, and someone swing this light source in circle. It seems that this light source is brighter. Yes or no
It may be truly a question of life and death.
You know those glow sticks.
As a sailor it is a good idea to carry one on our lifevest.
Falling into the sea, those glow stick make a light source that ...
