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2 votes
0 answers
45 views

Can nonimaging optics concentrate heat to a higher temperature than the source? [closed]

Practical goal: I'd like to concentrate the low-grade heat from the back of solar panels, which I've measured is in the range of 20-50F greater than the ambient temperature throughout the day, and ...
timblack1's user avatar
3 votes
3 answers
158 views

Can small solid bodies emit radiation with wavelength larger than the body itself?

It's known that EM waves cannot pass the aperture with a diameter much smaller than the wavelength. How is it for an opposite situation? If, for example, a solid body is a $100 \ \text{nm}$ sphere, ...
tynblpb's user avatar
  • 31
1 vote
0 answers
76 views

Focusing blackbody light simulation

As an honest citizen, I do not intend to violate the laws of thermodynamics by concentrating the light emitted by a blackbody on a smaller area. However by playing with this wonderful 2d ray online ...
Alexis Gros's user avatar
1 vote
1 answer
38 views

What will happen if the inner walls of the perfect blackbody (shown in the image) is made perfectly reflecting?

I am curious about making the inner walls of this blackbody perfectly reflecting instead of perfectly absorbing. If I keep on giving in incident radiation,the photon density inside will increase, ...
Mathew_'s user avatar
  • 538
1 vote
0 answers
105 views

probability of emission vs absorption in thermal radiation

I am trying to make sense of the thermal radiation emitted by a gas. The radiative transfer equation is $$\frac{dI}{dx} = \epsilon - \kappa I,$$ where I is the intensity, $\epsilon$ is the ...
courno's user avatar
  • 323
-1 votes
1 answer
42 views

How many degrees Celsius/Fahrenheit can be reached in 1 square meter area using magnifying glasses?

The magnifying glasses are each 10 meters in diameter, their collected light is concentrated via mirrors into a 1 square meter spot. Is it possible to get a temperature higher than 2000 degrees ...
Ellie Stewart's user avatar
3 votes
1 answer
2k views

Can you use sun light to heat an objects surface to hotter than the surface of the Sun? [closed]

I was reading this question: Concentrating Sunlight to initiate fusion reaction and some of the comments, as well as an answer, suggest that thermodynamics second law prevents what I ask in the title. ...
user273872's user avatar
  • 2,623
3 votes
1 answer
941 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 ...
kfs's user avatar
  • 63
6 votes
5 answers
505 views

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 ...
Selene Routley's user avatar
0 votes
1 answer
150 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 ...
Vial's user avatar
  • 594