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What does it mean in astrophysics for X-rays to be reflected?
Various articles about black holes talk about X-rays emitted near the
event horizon 'reflecting off the accretion disc'. What kind of material is it that can *reflect* X-rays? I've worked in X-ray crystallography, and we needed grazing incidence off very precisely figured monocrystalline silicon to get something that reflected X-rays at 12.7keV (selenium K line); astrophysical X-rays seem to be more at iron K which is about half that energy, but still generally-occuring materials either absorb or transmit them. Is this in fact more like the process around a nuclear detonation, where things absorb X-rays and are themselves heated to X-ray-emitting temperatures? Tom [[Mod. note -- Yes, thermal re-emission is one possibility. Compton scattering is another possibility. As you note, coherent reflection seems unlikely. -- jt]] |
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What does it mean in astrophysics for X-rays to be reflected?
In article ,
Thomas Womack wrote: Is this in fact more like the process around a nuclear detonation, where things absorb X-rays and are themselves heated to X-ray-emitting temperatures? The emission lines people talk about are X-ray fluorescence from (relatively) cold material. Martin -- Martin Hardcastle School of Physics, Astronomy and Mathematics, University of Hertfordshire, UK Please replace the xxx.xxx.xxx in the header with herts.ac.uk to mail me |
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What does it mean in astrophysics for X-rays to be reflected?
On Mon, 14 Jan 2019, Thomas Womack wrote:
generally-occuring materials either absorb or transmit them. [[Mod. note -- ... As you note, coherent reflection seems unlikely. Does not radiation reflection *always* consist of absorption & re-transmission? By "coherent reflection", JT seems to imply preservation of the original photons. But photons don't "bounce" in the rubber-ball sense, right? I'm reminded of transferring money in the banking system -- it's not the same dollar that moves around, money is "fungible" in the sense that a dollar has no individual identity as such. I am suspecting that photons are fungible in the same way, but that that element is not built into the model of light as we know it. [[Mod. note -- My apologies for being unclear. What I was trying to get at with the phrase "coherent reflection" (which in hindsight was a poor choice of words on my part) was "reflecting like a beam of optical light from a mirror, with angle-of-reflection = angle-of-incidence". As to whether elastic scattering of any sort yields the "same" photon, I suspect that you're right and that photons don't have an individual identify. In fact, I suspect that "the same photon" isn't even a meaningful concept in quantum optics. But my knowledge of quantum optics is alas very small, so I can't speak with any authority on this.... -- jt]] |
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What does it mean in astrophysics for X-rays to be reflected?
In article ,
Eric Flesch writes: As to whether elastic scattering of any sort yields the "same" photon, I suspect that you're right and that photons don't have an individual identify. Doesn't this have to be true? Wouldn't the Planck law have a different form if photons were distinguishable? When I studied thermodynamics, there were four cases: particles could be distinguishable or indistinguishable, and they could or could not occupy the same state. (Distinguishable particles that can occupy the same state are rare.) -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
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