All Questions
Tagged with electromagnetic-radiation temperature
73
questions
10
votes
3
answers
2k
views
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
0
votes
2
answers
62
views
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
0
votes
3
answers
218
views
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
0
votes
1
answer
109
views
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
1
vote
1
answer
187
views
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
3
answers
130
views
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
1
vote
2
answers
46
views
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 ...
3
votes
2
answers
246
views
Understanding blackbody radiation
I am studying blackbody radiation and modelling a cavity as a blackbody. However, I am encountering a number of confusions in this description:
Many textbooks mention that the cavity consists of ...
- 433
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
2
votes
2
answers
166
views
Why can't a reflective barrier raise an object's temperature past a heat source's temperature?
Say I have a 1 $m^2$ source of visible light emitting 1,000W worth of light. This is shining down upon 1 $m^2$ of ground.
If we treat the ground as a blackbody, my understanding is that eventually it'...
- 1,225
6
votes
4
answers
775
views
Why can't fire heat something hotter than itself, but electromagnetic waves can heat something indefinitely?
Part of my question on Can a low-energy source/object heat a higher-energy object via radiative heat transfer? asked if a 100W lightbulb could heat a blackbody in a vacuum indefinitely, presuming ...
- 1,225
11
votes
3
answers
4k
views
Can the temperature of a body become lower than the temperature of the surrounding air?
In winters, frost is formed on the grass and wood and not on concrete roads.Temperature of frost is lower than the temperature of the surrounding air.So a question arises ""Can a body become ...
- 1,357
2
votes
1
answer
36
views
Is there a relationship between the electrical power supplied to a material and the emitted wavelength?
I have a graphite bar that is used in a vacuum furnace that serves as a heating resistor and the heat is provided by radiation, so I would like to know by knowing the electrical input power (240kW), ...
- 21
1
vote
1
answer
79
views
$Q$ Transfer via Radiation Formula
According to the formula:
$$
\frac{\Delta Q}{\Delta t}=\sigma\epsilon A T^4
$$
What does $T$ refer to in a situation where I am modelling the power of radiation from air of temperature to surface of ...
- 113
5
votes
6
answers
2k
views
Do all objects at the same temperature glow the same color?
Does Kirchhoff's law for heat radiation imply that all objects at the same temperature will glow the same color?
In other words, if a piece of molten iron glows the same color as my body, which ...
- 593