All Questions
Tagged with blackbody or thermal-radiation
1,722 questions
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What is the definition of the Rayleigh-Jeans tail?
I've read some papers using the term "Rayleigh-Jeans tail" but cannot find a general definition. I would infer from context that it refers to the blackbody emission spectrum in the range of ...
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Can plasmas be black bodies?
I have recently heard the claim that sun can not be composed of plasma because plasma can not be a black body.
I am an uneducated layman, I've seen a lot of people (laymen) deviate from accepted ...
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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 ...
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Why Doesn't the Stefan-Bolzmann Law Deter Controlled Fusion Engineers From Seeking Extreme Temperatures To Maximize the $nτT$ Triple Product?
The triple product figure of merit for controlled nuclear fusion, nτT (density * time * temperature) would seem to favor high density approaches over high temperature. Radiative loss goes up as the ...
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Doubt regarding rate of loss of heat due to radiation
My doubt is with regards to radiation emitted by a body and how we define the rate of loss/gain of heat due to the same.
For my question, let us consider a body of: * surface area A
...
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Application Of Kirchoff's Law In A Desert [closed]
Homework Statement::
Sand is rough and black so it is a good absorber and radiator of heat depending on temperature.
During the day, sand's radiation of the sun's energy superheats the air and causes ...
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430
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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:
$$\...
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Blackbody radiation as a stochastic process
Can one treat the blackbody radiation as a stochastic process of photon emission? If so, what stochastic process is it (perhaps a Poisson process?)?
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Unexpected difference in experimental and theoretical results in verifying Stefan's Law
This is an experiment as part of my Experimental Physics Course in college; it involves the verification of Stefan's Law.
The experiment is pretty simple. We essentially treat an incandescent bulb as ...
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Black body radiation formula and de broglie wavelength
While deriving blackbody radiation, we assume that a standing wave of a particular wavelength can have energy $E=nh\nu$, where $\nu$ is the frequency and $n=1,2,3...$, with probability $e^{-nh\nu/k_{B}...
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Building a house that is warm in winter and cool in summer [closed]
The Northern house architecture is strikingly different from that used in the South (I am not taking extreme cases, thinking more of Northern or Germany versus Mediterranean:
Thick layers of thermal ...
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Thermal noise phasor amplitudes are Rayleigh distributed. How are voltages at the antenna distributed?
Background.
Consider an ideal antenna. For ideal polarized thermal noise treated as a random phasor sum, bivariate Gaussian statistics apply to the resultant phasor (call it $\vec{v}$) that is ...
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Can we say that Black hole is a Black body?
I want to know if a black hole is a black body.I got this doubt while studying photoelectric effects.
I am an 11th grader.I would be glad to have your help.
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Effect of changing $\rm CO_2$-levels on cooling the desert at night
It is known (e.g. as mentioned in this popular article) that the reason why deserts cool down at night so much (to temperature below zero degrees celsius) is that there is much less humidity in the ...
- 7,554
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If all human skin tones have similar emissivity constants , how can dark skinned people absorb more radiation than lighter skin tonned people?
Let's say we have two people of similar skin areas but of different skin complexions, it is a known fact that all human skin tones have similar emissivity constants. Then from the Stefan-Boltzmann law ...
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Why can the hole of a cavity-hole model be considered a radiating blackbody?
It is easy to understand why the small hole of the cavity-hole model simulates an absorbing blackbody as almost all incoming radiation into the hole is captured. Why can we consider the hole an ...
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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, ...
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Would a black teapot midway between the temperatures of the tea and air cool down or heat up? If neither, then how do the 3 reach thermal equilibrium? [closed]
Say you had a matt black teapot with hot tea inside it but cool air around it. Originally, I’m guessing the matt black teapot should absorb more joules of IR energy than it emits per second. This is ...
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How would a three dimensional standing wave created inside a box look like?
While deriving Rayleigh-Jeans law, in order to make a standing inside a cube, a condition is put forward which says electric field must vanish when the EM wave hits a surface of the cube.
I want to ...
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Cavity and black body radiation
If one speaks of the fact that one gets blackbody radiation in good approximation by a cavity with hole, does one mean as blackbody this hole, i.e. the place where the radiation exits from the cavity? ...
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Physics of the convection oven
I don't understand how convection ovens can cook food faster than radiant heat ovens. Guides to convection ovens claim that they cook food 25-30% faster than radiant heat ovens, but do not really ...
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What do Maxwell's equations tell us about the ultraviolet catastrophe?
I have found it that in elementary discussions of black-body radiation, other than justifying electromagnetic waves should exist from Maxwell's equations, those equations are not used for anything ...
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How to add markers to IR photographs
I'm using an IR camera to identify thermal patterns.
The thermal images are similar to this [LINK] image.
I'd like to add markers to the area being measured to determine dimensions and normalize the ...
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The entropy given by stefan Boltzmann's law looks remarkably similar to the volume of the sphere; $S(T)=\frac{4}{3}\sigma T^3$
If I am not mistaken the entropy for a blackbody per unit area is given by:
$$S(T)=\frac{4}{3}\sigma T^3.$$
The volume of a sphere is given by:
$$ V(r) =\frac{4}{3}\pi r^3. $$
Is this coincidental? I ...
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Quantifying how much would Jupiter heat up if you accelerate Jupiter out of orbit around the sun using fusion candles? [closed]
So, I responded to a post of someone saying that you could turn Jupiter into a spaceship using fusion candles. I mentioned that doing so would dramatically heat up the planet, especially if you were ...
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Is cooling by infrared absorbing rectenna possible?
We know that every hot objects emits IR radiation.
We also know that plasmonic rectenna can absorb and convert IR radiation to electricity.
Question: what will happen if we put an hot object inside a ...
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179
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How was the black body intensity vs wavelength (or frequency) radiation curve historically produced?
I have read that Wilhelm Wien gave his formula to match the radiation curve of a black body as shown in the picture; which works well in high frequency region. Another formula by Rayleigh-Jeans is ...
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Peak of energy and black body
The tungsten filament of an incandescent light bulb has a temperature of approximately 3000 K. The emissivity of tungsten is approximately
1/3, and you may assume that it is independent of wavelength. ...
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Black body side of the Moon
A few closely related questions regrading the Moon thermodynamics:
The Moon is clearly not a black body, as it reflects a great deal of radiation incident on it. Still, it does absorb some radiation ...
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Aren't all objects luminous in a sense?
In my physics class, I learned about "nonluminous objects" - these are objects which don't produce their own light. But, don't all objects emit light by black body radiation? So are all ...
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Why does the ground-state energy of the quantum harmonic oscillator result in ultraviolet catastrophe? [duplicate]
Background - This post is closely related to this question.
Planck considered that the electromagnetic waves inside a cavity are standing waves due to oscillating charges on the wall of the cavity. At ...
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Deriving Wien's approximation
Without Planck's law from where and how could one empirically get this.
Could it be got from power is proportional to fourth power of temperature.
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Planck's assumptions for treatment of blackbody radiation
Planck, in his treatment to solve blackbody radiation, considered that the electromagnetic waves inside the cavity of the blackbody are standing waves due to oscillating charges on the wall of the ...
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356
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Equilibrium in blackbody radiation
I was reading this post and I think I am still confused. A blackbody $radiator$ is not in equilibrium, by definition, since it is radiating. If so, why does the blackbody spectrum accurately describe ...
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Emissivity of a perfect reflecting body
So from thermal classes, we kept saying reflectance + emissivity = 1, and thus for a perfect reflecting body, there's zero emissivity. But what about a reflecting body that is heated internally?
Say ...
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Planck's Law notation
I have just picked up the book Elementary Quantum Mechanics by Peter Fong, and on the first page he writes Planck's law as $$u(\nu)d\nu=\frac{8\pi h \nu^3}{c^3}\frac{1}{e^{h\nu/kT}-1}d\nu$$ where $u(\...
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I’m studying black body radiation and I can’t understand how it produced due to the vibrations of atoms
So,in my physics school book it’s written that atoms don’t radiate as long as they are stable ”in the ground state” I can’t understand how I mean isn’t all the bodies radiate as long as they have a ...
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What makes a lightbulb glow?
I am self-studying electricity and magnetism, and I am confused about a point.
I have learnt that the drift speed of an electron is extremely small. However, according to Drude's model, the electron ...
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Deriving black body law from fluctuation-dissipation theorem?
Is it possible to prove the Blackbody radiation law using the fluctuation-dissipation theorem?
Has it been done, or is there some reason why it wouldn't work? I would appreciate if you could point me ...
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How does thermal wavelength work exactly?
In many sources it is stated that the thermal wavelenth indicates the rough size of the atom. It is then stated that this wavelenght is the de-Broglie wavelength of a particle with a momentum with the ...
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Does radiant heat energy increase the temperature of any gases it passes through?
I am in an HVAC/R technician certification class, and the instructor taught us that radiant heat energy only increases the temperature of solid objects, and the temperature of gases are not affected ...
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Building orientation - how come both summer and winter solstice used for a facade?
I am planning to build a shed atop my terrace. I was analyzing the sun path to determine the overhang length, facade height etc, but got stuck with a conflict as below.
The summer sun's location peaks ...
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Is Thermal radiation emitted by a blackbody some photons
If a blackbody absorbs all radiation
and emits some due to it's heat, then is the thermal radiation actually some photons that are not in the visible region?
Can there be a blackbody that emits ...
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Why does wien's law only apply to blackbodies?
thinking about it the sun is just made of atoms ,
if it absorbs or not it's different ? i don't exactly know how to word it;
just why only things that absorbs all radiations are valid in wien's law
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Is it possible to explain the Ultraviolet Catastrophe as a manifestation of the Riemann-Lebesgue Lemma? [closed]
Is it possible to explain the Ultraviolet Catastrophe as a manifestation of the Riemann-Lebesgue Lemma?
I don't fully understand any of both topics, but reading about the Ultraviolet Catastrophe on ...
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Long temporal coherence sunlight
What is the reason that sunlight have short temporal coherence? I know everybody says that coherence length is inversely proportional to bandwidth. Does it mean that if sunlight passes through a very ...
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Will stainless steel heat up faster than a cordierite-based surface in a gas oven?
Background:
As some may know, pizza stones, used to accumulate heat before the
pizza dough is put into the oven, are often made of cordierite. If
it's well heated it should provide the underside of ...
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Gas to solid heating?
I am doing a study on the phenomenon of pyrolysis. This is purely a study of the underlying physics. Generally, in practice, pyrolysis feedstock is heated conductively but we are examining the energy ...
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Why while deriving Rayleigh Jeans law in this book, an EM wave is divided into its components along the three axes & how is the math formed?
An EM wave making arbitrary alpha, beta and gamma angle with x,y and z axes respectively is divided into its components along the three axes? What does it even mean? If the components along the three ...
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Comparing the variance of the position of particles of a sample of matter with the sample's temperature
As the title suggests i have attempted comparing the variance of the position of particles of a sample of matter with the sample's temperature.
Now firstly we need to clarify the basics:
method for ...
