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I am not asking for too many experimental details. Just give me a rough idea of what things could one measure using which instruments so that the ultraviolet catastrophe (Rayleigh-Jeans law) could be refuted. Also, how does one experimentally verify the Planck's radiation spectrum? Assume me to be a senior undergraduate while explaining things.

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  • $\begingroup$ Umm... your eyeballs with an object that's hot? Infinite energy emission is a problem. $\endgroup$ – user121330 Oct 27 '17 at 1:21
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    $\begingroup$ So ... the thing here is that the prediction is so outrageous that it was refuted before it was ever made, There are at least three classes of measurements that come to mind and any of them could be done multiple ways. $\endgroup$ – dmckee --- ex-moderator kitten Oct 27 '17 at 1:24
  • $\begingroup$ @user121330 I have just expanded my question about Planck's law. Can you please reply? $\endgroup$ – Sashwat Tanay Oct 27 '17 at 1:27
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    $\begingroup$ "How can one experimentally refute the ultraviolet catastrophe" - it's called a catastrophe for a good reason. When such seemingly reasonable scientific principles unambiguously lead to a nonsense result, that a black body in thermal equilibrium at finite temperature radiates 'infinite' power, there's no question of experimental refutation. That fact that we exist refutes it thus. $\endgroup$ – Alfred Centauri Oct 27 '17 at 2:55
  • $\begingroup$ @Bingo Ask a new question. It's a little rude to pull the rug out from under the people who've already answered. $\endgroup$ – user121330 Oct 27 '17 at 17:32
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No instruments required. Turn on a light bulb and note that everything around it does not catch fire, vaporize, or turn cancerous. According to the Raleigh-Jeans law, an object with greater than zero temperature should emit more power at higher frequency light. However much power is emitted as visible light, more power should be emitted as ultraviolet light, still more as X-rays, and on and on. This leads to an infinite amount of power being radiated from all objects that are hotter than absolute zero. Obviously, this does not happen.

As for measuring the real spectrum of black bodies, it's a matter of separating the different wavelengths of light and using a photometer or photodiode to measure the power of each. The separation can be done with a diffraction grating and the measurements done at different angles, or with series of narrowband filters.

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  • $\begingroup$ Thanks, @Mark H I have expanded my question to verify Planck's radiation law. Do you have anything to say about it. $\endgroup$ – Sashwat Tanay Oct 27 '17 at 1:26
  • $\begingroup$ @Bingo Answer updated. $\endgroup$ – Mark H Oct 27 '17 at 2:05
  • $\begingroup$ for experiments , there are a lot if one googles example :phys.ksu.edu/personal/rprice/BB.pdf $\endgroup$ – anna v Oct 27 '17 at 3:33

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