All Questions
17
questions
-1
votes
2
answers
152
views
Max Planck - what does 'per wavelength' mean?
Planck says
$$B_\nu(T)=\frac{2hc^2}{λ^5}\,\frac{1}{\mathrm{e}^{hc/λk_BT}-1}.$$
It's defined as energy emitted per unit volume per wavelength. I'm not sure if this includes per solid angle, but I ...
- 200
0
votes
1
answer
110
views
Max Planck - what's the $B$?
Planck says
$$B_\nu(T)=\frac{2\nu^2}{c^2}\,\frac{h\nu}{\mathrm{e}^{h\nu/k_BT}-1}.$$
It is power emitted per unit area per unit angle per unit frequency. This is what I'm curious now.
Let's say we ...
- 200
0
votes
4
answers
274
views
How does blackbody radiation suggest the quantization of energy?
I have read about Wein's law and Rayleigh-Jeans law which were apparently based on classical mechanics and couldn't explain the radiation spectrum of a blackbody.
Then Planck came up with the ...
- 1,305
0
votes
0
answers
50
views
Why does the Planck curve drop below the Rayleigh-Jeans curve for blackbody radiation when Planck quantized the energy?
This has been a research topic of mine for days now. I understand the Rayleigh-Jeans law and how it leads to the ultraviolet catastrophe. I have been searching for a clear, conceptual explanation of ...
- 434
1
vote
2
answers
323
views
Thought experiment on temperature dependence of black body radiation
There's a very famous thought experiment that verifies the temperature dependence of blackbody spectra
The proof first assumes that two blackbodies have different spectra and then shows that this ...
- 1,638
33
votes
3
answers
5k
views
Force of photons from the Sun hitting a football field = weight of 1 dime?
I read, I think, some time ago that the "weight" of photons from the Sun hitting an area the size of a football field at noon on a sunny day would be about the "weight" of a dime?
...
- 447
12
votes
4
answers
6k
views
How to identify if a photon comes from the sun?
Is there any way to know whether a group of particles is generated from the sun rather from an artificial source?
- 137
1
vote
0
answers
35
views
Is my understanding of thermal equilibrium of radiation correct?
In the description of a container with a hole as a blackbody, in Peter Atkins | Julio de Paula - Physical Chemistry, It's given that
"the container with pin hole emits radiation that can be ...
- 21
2
votes
0
answers
47
views
Emissions from a Blackbody and the UV Catastrophe
Recently I found myself becoming confused over a topic that I thought I had previously understood.
In a theoretical blackbody which reaches thermal equilibrium the energy absorbed is equal to the ...
- 207
3
votes
2
answers
541
views
Do photons exist at all possible wavelengths? [duplicate]
My question refers to Photon flux spectrum diagrams.
The diagram shows the number of photons at different wavelengths. My question is whether the graph is granular or continuous. Do photons exist at ...
- 227
2
votes
1
answer
411
views
What was Planck's motivation for the frequency dependence in $E=nh\nu$?
Many accounts of the history of quantum physics explain how Planck resorted to quantizing energy in an "act of desperation" while attempting to solve blackbody radiation, only to discover by surprise ...
- 3,407
2
votes
1
answer
1k
views
What is the distance between photons?
In the book of The First Three Minutes by Weinberg, at page 69, he states that
We also saw that the decrease in the energy density of black-body
radiation at long wavelengths is due to the diffi- ...
- 2,283
6
votes
2
answers
477
views
Very old photons from the Sun
While watching the rebooted Cosmos series, I heard Tyson say that a photon arriving to the Earth from the Sun might be millions of years old.
If I understood correctly, once it's emitted inside the ...
- 519
1
vote
2
answers
732
views
UV catastrophe - why a problem?
Ultra violet catastrophe happens when we integrate the Rayleigh Jeans spectral density over all frequencies to calculate the total energy, which yields:
$$ \int_0^{+\infty} \frac{8\pi \nu^2}{c^3} k_B ...
- 24.9k
2
votes
1
answer
2k
views
Why do heated bodies produce continuous spectra? [duplicate]
I have read most of the answers as to why the Sun produces a continuous spectrum, but I can't understand the main point underlying the explanation
I mean, say we have gaseous iron and solid one, ...
- 103