All Questions
Tagged with absorption thermodynamics
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Regarding the absorption property of a blackbody
Consider a blackbody of surface area $S_b$ and at temperature $T_b$. It is placed inside an evacuated chamber (to neglect all the effects of convection), with walls of chamber at temperature $T_c$ and ...
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Where does light energy end up? [closed]
Here's a gedankenexperiment:
In situation A you run $P$ watts of incandescent bulbs in a closed room for time $t$ (light and heat cannot escape the room). The room starts a temperature $T$ and ends at ...
- 147
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Heating of a metallic 'gray body' by radiation
I am interested in a realistic model for calculating the heating of a metallic body by solar radiation.
Assumption (0) is vacuum, so neither conduction nor convection.
Assumption (1) is integration ...
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Is a layer of gas with sufficiently large optical thickness really radiating as a black body?
Can a parcel of gas with large value of optical thickness really radiate like a black body?
I have in mind a simple (most likely oversimplified) model which yields
$$I_\nu = I_\nu(0) e^{-\tau\nu} + I_\...
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Why can Einstein coefficients be derived based on thermodynamically equilibrium relations when they are basically intrinsic?
Einstein coefficients for emission and absorption ($A_{21}$, $B_{12}$, $B_{21}$) are often derived from a consideration of thermodynamic equilibrium using Boltzmann statistics and comparison with ...
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Converting light into heat/movement, reflection vs absorption
at school we had a small device in a glass dome it had 4 plates every plate was blackened on one side and silver colored on the other side. when the sun did shine on one side of it, it would start to ...
7
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1
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Could the solar shield on the James Webb telescope have been pitch black or does it need to be highly reflective?
When I look at pictures of the sun shield on the James Webb Space telescope (JWST), I see something that looks highly reflective (and hence must have a very low emissivity). My intuition tells me that ...
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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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146
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Why do Greenhouse Gases absorb heavily in certain wavelengths? [closed]
What molecular properties make greenhouse gases absorb and reemit primarily IR radiation? That is, why are CO2, H2O and NO2 all greenhouse gases (GHGs), but others (such as helium and neon) aren't? ...
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Absorption spectra Oxygen vs temperature
Whilst recently commissioning a spectroscopic Tunable diode laser "Oxygen Analyser" on a waste-to-energy plant, I wondered how the Analyser (which fires a narrow wavelength laser across the ...
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2
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Absorption vs emission not in thermodynamic equilibrium
I have read that good absorbers are good emitters. The argument goes that at thermodynamic equilibrium, the amount of radiation a body emits must be the same as it absorbs, otherwise the body will ...
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Possibility of combining photovoltaics and solar thermal energy
In a private setting, photovoltaics and solar thermal energy are often harvested on the home's roof and roof area is limited. So, I thought about combining both, i.e. mounting solar collectors ...
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204
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How to calculate absorbed heat by different painted colours on a steel container?
I'm looking to understand how I can calculate the heat impact in a galvanized steel box with a cooling capacity of $0.25\;\mathrm{kW}$.
For example, what is the heating absorption of a box painted ...
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482
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Thermal radiation vs emission spectra of gases
I am a high school student and I am very confused in absorption and emission spectrum of gases, for e,g take hydrogen at room temperature for simplicity, so that we can talk in terms of Bohr's model ...
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If black is the best absorber and radiator, why does it get hot?
I can guess that it’s emission peaks at a higher temperature than white. So when a light is turned onto a black and white piece of paper, the initial condition is not at equilibrium. As black absorbs ...
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