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...couldn't I use a retarding film of randomly varying thickness to convert a Coherent laser beam into an incoherent laser beam to improve eye safety? Absolutely not. A beam's destructiveness to the eye depends on three things: Energy delivered to retina and the time periods it is delivered over, quantified by the ISO60825 concept of Maximum ...


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Couldn't I use a retarding film of randomly varying thickness to convert a Coherent laser beam into an incoherent laser beam...? If the film is not changing (in time) you are not changing the coherence properties of beam at all. You can think of putting a slab of something in the way as putting a really bad lens (possibly with no optical power) in the ...


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I hope someone with more knowledge will pop into thread, but here is my education. There might be number of ways to measure such low temperatures. One I find fascinating is starting with material, namely Bose-Einstein condensate. Reference is this one: Cooling Bose-Einstein Condensates Below 500 Picokelvin, Leanhardt et al. Science, 12 September 2003. ...


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The temperature is not measured in the sense of using a thermometer. Instead it is calculated from the velocities of the particles in the trap. Temperature is related to the velocity distribution by the Maxwell-Boltzmann equation. Under normal circumstances we are usually starting from a known temperature and calculating the velocity distribution. However ...


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This answer was written for another question that was deleted a few minutes ago. I decided to post it here even though the effect it describes duplicates Floris' answer: Photons passing through a medium don't just punch their way through like bullets. They are absorbed by the atoms of the medium and then re-emitted. (Incidentally, the reduction in speed ...


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What you can do is find out the illuminance (lux=lm/m2) of a magnitude 6 star, which is the limit of human vision of light spots and see what luminous flux (lm) creates that illuminance at your certain distance from the spot, assuming that the light disperses uniformly in a semisphere (unless you have better information on the light distribution). From the ...



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