All Questions
Tagged with optics thermal-radiation
39
questions
21
votes
7
answers
5k
views
What can we deduce by the fact that mirrors cannot get a ray hotter than Sun's surface?
I think it is quite counter-intuitive that some lenses or mirrors focusing sunlight to a single spot cannot produce a temperature higher than Sun's Surface.
What could a scientist deduce from that ...
- 737
1
vote
2
answers
3k
views
Sunlight and Moonlight are coherent or not?
I have tried a lot to find the exact answer for this question but unfortunately couldn't get it. If Sunlight and Moonlight are coherent then What could be the reason behind this?
- 21
3
votes
1
answer
886
views
Einstein Coefficients: What is the justification for absorption, spontaneous and stimulated emission reaching equilibrium?
In Einstein's derivation of the Einstein coefficients, he applied the condition for equilibrium on the two populations of atoms in processes of absorption, stimulated and spontaneous emission.
In ...
- 63
2
votes
2
answers
274
views
How black body absorbs light?
I learn that black body absorbs light, but couldn't get the mechanism behind it. I wish I could get help.
- 107
6
votes
5
answers
494
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Light Polarizer and the Second Law of Thermodynamics
I have stumped myself with a thought experiment of my own devising.
Suppose I take a beam of wholly depolarised, but otherwise plane wave light. Its von Neumann entropy per photon is $\log(2)$ nats ...
- 88.5k
0
votes
1
answer
147
views
Radiation pressure thermodynamic paradox
Could the radiation pressure of a black body (theoretically) perform work on the perfectly reflecting apparatus in the figure below? Assume that the block does not hinder the passage of light through ...
- 584
1
vote
1
answer
138
views
Intensifying a light source using black body concept
Is it possible to intensify light by initially passing it through an apparatus like a perfectly black body and then through a colloidal solution?
What kind of material can be used inside the ...
- 19
3
votes
0
answers
110
views
A problem concerning the change of temperature and spectrum of a filament
The spectrum of a filament has been given before, the left one having the lowest temperature, the middle with a medium temperature and the right one with the highest. My question is this: Why does the ...
- 165
0
votes
4
answers
4k
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How to get Intensity over a range of wavelengths from a Total Intensity
This is a theory vs experiment problem for me I think in that - as usual - I think I know the theory, but when it comes time to run an experiment, I can't actually extract squat.
So, here is my light ...
- 631