All Questions
Tagged with optics thermal-radiation
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Radiation energy and momentum relation [duplicate]
Why is $\rho = 3p$ for radiation? What is the intuition behind this? If we had only 2 spatial dimentions, would it be $\rho = 2p$?
(I came across this relation while studying the state of the universe,...
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How to measure light intensity in a room?
Does anyone know how I would go about measuring the light intensity in a room? I'm not interested in knowing the lux reading, I would like to measure the $W/m^2$ due to thermal radiation in my ...
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Any research or study that monitored the spectrum of the natural light during the entire day?
I am interested in understanding the light spectrum during sunrise, morning, midday, afternoon, golden hour, and blue hour.
Is there anyplace I can look at those?
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Need clarity behind the theory of diffraction for a black-body source
Attempting to model the diffraction for a black-body source, I have stumbled upon a bit of a conundrum with the mathematics. I am not asking WHY the light is diffracted, but instead looking for a ...
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Power received close to a large black body radiator
I am interested in calculating the power received by an object near a black body radiator. Say, for example, I had a piece of paper perpendicular to the earth's surface normal. If I make assumptions ...
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How is the Kelvin temperature of a light source or an image is calculated?
I searched for it but couldn't find any answer for this.
For a light source is it simply the average of the full spectrum power?
And how do you compute it for an image? How can you tell the difference ...
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Photon statistics for thermal light?
I know that the variance $\Delta^2$ of the number of photons $n$ for thermal light is:
$\Delta^2 n = \bar{n} + \bar{n}^2 \hspace{2 cm} (1) $
where $\bar{n}$ is the average number of photons.
This ...
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Focusing blackbody light simulation
As an honest citizen, I do not intend to violate the laws of thermodynamics by concentrating the light emitted by a blackbody on a smaller area. However by playing with this wonderful 2d ray online ...
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What would a piece of high emissivity polished metal inside a blackbody cavity look like? Darker than the walls of the cavity but the same color?
I'm trying to work out the challenges to using an infrared pyrometer to measure the temperature of a piece of shiny metal. This device has no user-accessible emissivity setting, and my sample will ...
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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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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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Why does cooling down thermal imaging cameras increase sensitivity?
A lot of high-sensitivity thermal cameras and sensors are (cryogenically) cooled down to low temperatures to achieve these high sensitivities. For example. the Stinger missile, and the James Webb ...
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How does incandescent lamp mounting influence color temperature?
I have a high power incandescent halogen lamp, which I want to mount behind a pane of glass some distance away, such as to minimize that funky burning dust smell, that I really dislike.
Now say this ...
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What is the wavelength of white light? [closed]
Does white light have a wavelength, and I know that the sun emits white light, but the atmosphere makes it refract to make it appear yellow to us. Do all the stars in the universe emit white light?
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Does a thermal camera detect distant objects colder?
Thermal cameras are often calibrated and display the temperature color-coded in $^\circ$C and I wonder how that works...
A black body emits photons because of it's thermal energy. The hotter it is, ...
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Why does a thermal camera see contours?
A thermal camera is sensitive for photons in the $\mu m$-range and thus for the heat that objects emit. However, I realized that you can often see the "visible" image in thermal camera ...
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Planck on the entropy of light
While reminiscing of his discovery of the quantum of action Planck writes in his "Scientific Autobiography" [1]:
Thus the nature of entropy as a measure of probability, in the sense ...
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Why does the sky after sunset mimic the blackbody spectrum?
There are several answers on this site and elsewhere about why the sky is blue and why sunsets are reddish. But I could not find anything that discusses the relationship between the blackbody spectrum ...
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Why are infrared images not great?
Why are infrared images not great?
Simply googling infrared images, and looking at pictures of things like streets, people, animals, etc. . . I can't quite pin ...
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Kirchhoff's law for glass and transparent crystals; how exactly do hot transparent materials produce so much visible thermal radiation?
Together, the current answers to Is the visible light spectrum from "red-hot glass" at least close to Blackbody Radiation? explain that while we can not necessarily call a heated sample of ...
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What could be and how to come up with a mathematical formula for the local electric field inside a blackbody cavity?
I asked a similar question here more than two years ago. I did not get an answer to my complete satisfaction. I would like to reiterate the problem again.
The local electric field of a monochromatic ...
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probability of emission vs absorption in thermal radiation
I am trying to make sense of the thermal radiation emitted by a gas.
The radiative transfer equation is $$\frac{dI}{dx} = \epsilon - \kappa I,$$ where I is the intensity, $\epsilon$ is the ...
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How many degrees Celsius/Fahrenheit can be reached in 1 square meter area using magnifying glasses?
The magnifying glasses are each 10 meters in diameter, their collected light is concentrated via mirrors into a 1 square meter spot. Is it possible to get a temperature higher than 2000 degrees ...
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How far can we track ionic based spaceships if antenna fails
Suppose we send an ionic based spaceship and all the antennas are broken on launch,
suppose the spaceship destination is another solar system.
Obviously we can track it with optical telescopes,
but i ...
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Why doesn't the moon appear yellow?
The sky is blue (I'm told) because nitrogen in the atmosphere scatters short blue wave lengths of light from the sunlight, which is also why the sun appears somewhat yellowish rather than white, as it ...
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How can a solid be thermally transparent?
Thermal cameras designed to image wavelengths between 7-14µm (which is the peak for blackbody radiation around "room" temperatures) use lenses made of germanium, zinc sulfide, zinc selenide, or ...
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Can you use sun light to heat an objects surface to hotter than the surface of the Sun? [closed]
I was reading this question: Concentrating Sunlight to initiate fusion reaction and some of the comments, as well as an answer, suggest that thermodynamics second law prevents what I ask in the title. ...
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Do optical filters emit thermal radiation at filtered frequencies?
So as the title says. Do optical filters emit thermal radiation at frequencies they are supposed to block or at frequencies they are supposed to let trough? Or does their spectral absorption property ...
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Why do metals only glow red, yellow and white and not through the full range of the spectrum?
Why don't metals glow from red to yellow to green to blue etc.? Why only red, then yellow and then white? Shouldn't all wavelengths be emitted one by one as the temperature of the metal increases?
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Breit–Wheeler γ γ′ → e+ e− pair production with hohlaraum as photon target; is this particular experiment going to be carried out?
The IFLScience article Scientists Work Out How To Make Matter From Light describes photon-photon collisions producing pairs of particles, and the Nature Photonics Letter A photon–photon collider in a ...
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