All Questions
Tagged with electromagnetic-radiation thermodynamics
179
questions
10
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3
answers
2k
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What do we mean when we say the CMB has a temperature and how do we measure it?
I have read this:
An object without any internal degrees of freedom, like a single photon, can't really have a temperature. But an ensemble of photons can have a temperature. If you put an ensemble ...
- 29k
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0
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21
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What is the relationship between the applied reverse bias in a p-n junction to the band gap of the semiconductor?
Consider a p-n junction under reverse bias. The difference in the Fermi Energy of the p-side and the n-side is $qV_r$ where $q$ is the elementary charge, and $V_r$ is the applied reverse voltage. What ...
- 1
0
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2
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62
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Why are planets cold?
Excuse me for me ignorance, I'm just fiddling around this question for quite a while.
The question of course is not limited to planets. Boiling down to, why isn't the universe heated up by now to ...
- 101
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2
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49
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Can a region of electromagnetic waves alone be considered a thermodynamic system? Can work and heat interactions be made sense for them?
Consider an ideal antenna producing coherent radio waves, and suppose the waves are not received by any body (they are sent off to space). Can we say a work interaction/transfer has been done? Or is ...
- 8,640
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45
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Electromagnetic entropy maximum in Planck's black-body radiation law
I am reading Planck's work on black-body radiation.
In the paper on the page 19 it is said that the expression
$$R_\nu=\frac{\nu^2}{c^2}U\tag1$$
where $R_\nu$ is the intensity of a linearly polarised ...
- 443
0
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3
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215
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Is heat basically infrared?
Particularly given the fact that heat can propagate through a vacuum in the form of infrared radiation. But is the modern theory of heat based on the notion that heat in the matter(regardless of its ...
- 439
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1
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60
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Solving Maxwell Equations when a charge is put inside a generic conductor
A net point-charge density $\rho_0$ is impressed without speed (no impressed current density) at position r0 at time $t_0$. Relaxation analysis tells us the charge density will decrease exponentially ...
- 1,319
1
vote
1
answer
47
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Doppler broadening upon reflection from liquid interface
I just came across the question "Why are the surfaces of most liquid so reflective?", in which the author asks how the surface of a liquid gives rise to a mirror image, even though it ...
- 3,260
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1
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108
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How can we prove mathematically that a body not at zero kelvin emits radiations of all wavelengths?
Well, today our teacher was taking up the topic Radiation under the chapter Properties of Matter. And he said that all bodies with a temperature above zero kelvin emit EM waves with all wavelengths ...
- 23
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votes
1
answer
99
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Light, Work, and the 2nd Law
I am trying to figure out what restrictions there are on converting light energy into work.
I understand that solar energy can be converted to electrical energy with roughly 90% Carnot efficiency. ...
- 13
1
vote
1
answer
184
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Can something become hot enough that it stops glowing?
So I understand that matter emits EM waves when hot. And that the higher the temperature, the shorter the wavelength, so cooler flames start off orange and the hotter flames reach light blue and white....
- 131
0
votes
4
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136
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Why does a blackbody object emit light if it only absorbs light?
I have learned that a blackbody object only absorbs light and thus does not reflect any light. The blackbody object will, however, emit light, and none of this light is due to reflection. Where does ...
- 461
1
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0
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31
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What is the entropy increase associated with the absorption and remission of solar radiation? [duplicate]
The average solar irradiance over the Earth is 1361 W/m2 with a wavelength distribution given by Planck's law for a temperature of about 5778 K. Approximately, the same amount of radiation is re-...
- 1,640
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votes
3
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128
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Is it possible to raise an object's temperature by reflecting or absorbing and re-radiating its own radiation back on it?
I am a layman with a little beginners knowledge.
This question is an effort to prove or disprove the Greenhouse Effect (GHE) theory as this is the basis of "back radiation" as described by ...
- 11
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2
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Thought regarding Newton's law of cooling [closed]
I learnt that when a body cools by a small temperature say 5-10 k, from T1 to T2 we can approximately write rate of decrease in temp as c ((T1+T2)/2 - To) c is a constant
To representing surrounding ...
