# Tagged Questions

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### How damaging is light?

On Surely You're Joking Mr Feynman, when talking about the Trinity test, the author states: the only thing that could really hurt your eyes (bright light can never hurt your eyes) is ultraviolet ...
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### Index of refraction appearing in the radiative transfer equation

In this publication the Radiative Transfer Equation (RTE) (eq. (7)) contains the following emission term: $$n_i^2\kappa_{d,i}L_{b,i}(\mathbf{r})$$ where $n_i$ is the refractive index of component ...
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### Maintaining local thermodynamic equilibrium (LTE) in radiating gas with a broad atomic transition line

Definitions / Background In LTE, Kirchoff's law for radiation holds: $$\frac{j_{\nu}}{\alpha_{\nu}} = B_{\nu} (T)$$ where $j_{\nu}$ is the specific radiative emissivity, $\alpha_{\nu}$ is the ...
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### Absorption cross section and absorption coefficient

What is the absorption cross section, how is it measured? How to convert it to the absorption coefficient (measured in cm$^{-1}$)?
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### Absorption coefficient from HITEMP or HITRAN [closed]

How to calculate the absorption coefficient (for radiation) from HITEMP or HITRAN databases? Or where can I find some tables or plots for the absorption coefficient?
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The equation for radiative transfer is $$\omega \cdot \nabla I = \kappa(B - I)$$ where $I$ is the intensity of radiation, $\omega$ is the ray direction, $\kappa$ the absorption coefficient, $B$ the ...
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### Could airport security devices detect differences between printed and written documents?

If airport security scanners of any kind (xray, thermal, whatever else they use) looked at two items: A printed paper textbook The same printed paper textbook into which we have inserted a regular ...
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### Why doesn't diamond glow when hot?

In an answer to this SE question, the respondent explains that heating a perfect diamond will not cause it to glow with thermal blackbody radiation. I don't quite follow his explanation. I think it ...
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### How does heat energy travel in space?

How does the heat energy from the Sun reach us on the Earth? Since the kinetic energy of an atom is the amount of heat energy and there is no matter in space, how does heat from the Sun reach us?
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### Definition of isotropy of radiation and its consequences

I have encountered different notions of isotropy of radiation and I would like to know if they are the same and what the exact definition of isotropy is, if one exists. Let's take black body ...
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### 2 ways to generate electromagnetic wave

According to Maxwell's equations, accelerating charges emit electromagnetic radiation. According to Quantum physics, heating causes electromagnetic radiation too. These 2 radiations, are they ...
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Why did scientists study black body radiations from something as complicated as a hollow container rather than the radiation from something simple like a thin solid cylinder?
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### Kirchhoff law of thermal radiation

Kirchhoff's law of thermal radiation states that for thermal equilibrium for a particular surface the monochromatic emissivity $\epsilon_{\lambda}$ equals the monochromatic absorptivity ...
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### Extreme heating by Sun on Earth- Can eggs be fried?

Will it be possible to fry eggs in Sahara desert by just keeping them under the sun? If so, then will the radiated eggs be any different? Or will we have to use the solar cooking concept to some ...
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### What is the relation between surface area and radiation, if any?

Basically I wonder what happens to emitted radiation by douubling a light e.g. twice the surface area of the sun will emit how much more radiation? 4 times more? Is there a formula?
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### How to interpret Stefan-Boltzmann's law?

The Stefan-Boltzmann equation states $e=\sigma T^4$, but how do we interpret this? Is this completely wrong: A body of size $s^2$ generates the radiation/temperature $T^4$ for a given size and a ...
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### A problem concerning the change of temperature and spectrum of a filament

The spectrum of a filament has been given before, the left one having the lowest temperature, the middle with a medium temperature and the right one with the highest. My question is this: Why does ...
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### Why are umbrellas black?

Why are umbrellas specifically in black? Of course we do have colored ones, but black is the majority. Is there any scientific reason behind it?
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### Wien's fifth power Law and Stephan Boltzmann's fourth power laws of emissive power

Wien's fifth power law says that emissive power is proportional to the temperature raised to the fifth power. On the other hand, the Stefanâ€“Boltzmann law says emissive power is proportional to the ...