All Questions
6 questions
4
votes
1
answer
238
views
Planck's catastrophe?
In deriving Planck's blackbody formula, the number density of normal modes (per unit frequency$^\dagger$) is found, given by
$$
N(\omega)=\frac{V}{\pi^2c^3}\omega^2,
$$
where $V$ is the volume of the ...
- 1,999
2
votes
1
answer
2k
views
What's the relationship between the energy density of a black-body and its radiant exitance?
Through a bit calculation we can derive that in a cavity, the energy density $$u(f,T)=\overline{E(f)}\times G(f)=\frac{8\pi h}{c^3}\frac{f^3}{e^{h\nu /kT}-1}$$
If we take the integral over all ...
- 1,188
2
votes
1
answer
4k
views
Is the quantum harmonic oscillator energy $E = n\hbar\omega$ or $E = (n + 1/2)\hbar\omega$? (Feynman Lectures)
Please, read the whole question. I've discussed a few contradictions and so far have not found an explanation for them.
I was reading The Feynman Lectures on Physics (vol. 1), the part where he talks ...
- 1,263
3
votes
3
answers
430
views
Why using a sum instead of an integral solves the Ultraviolet catastrophe?
Im reading about how using a sum instead of an integral when deriving the Rayleigh-Jeans law (in the equipartion part) solves the ultraviolet catastrophe. basically doing the following replacement:
$$\...
- 97
2
votes
3
answers
441
views
Why is the black body radiation independent of composition and incident radiation?
There have been questions similar to this, but most of them do not explain the mechanism responsible for the phenomena but instead explain through contradiction of second law of thermodynamics, for ...
- 659
1
vote
1
answer
2k
views
Black body radiation at atomic level [duplicate]
I need help in black body radiation. I know quantitative equations of black body radiation. what I need to know is what is happening inside a black body at atomic level. What I mean is, if light ...
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