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For centuries people argued whether light was particles or waves. Neither idea fit all the evidence.

I have the idea that all of the data that doesn't fit particles is about how light travels through space. For example the double-slit experiment.

And I have the idea that all of the data that doesn't fit waves is about how light interacts with matter. For example the photoelectric effect.

Am I wrong? Are there examples where the wave theory incorrectly predicts the pattern of radiation traveling through space?

Are there examples where particle theory incorrectly predicts how light interacts with matter?

Of course in modern physics it makes no difference. All we can measure is probability distributions, and quantum mechanics correctly predicts probability distributions. It makes no difference what interpretation we put on it when it correctly predicts the measurable results.

But do I have it right about the problems with the old theories?

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  • $\begingroup$ Are there examples where particle theory incorrectly predicts how light interacts with matter? What are the equations of “particle theory” and what do they predict for the photon/electron scattering differential cross section? $\endgroup$ – G. Smith Apr 13 at 20:35
  • $\begingroup$ @G.Smith I have no idea. Newton explained rules for light corpuscles traveling through space. They travel in straight lines. They bounce off mirrors at equal angles. Etc. It mostly worked but it didn't explain diffraction, particularly the double-slit experiment, etc. $\endgroup$ – J Thomas Apr 14 at 16:43
  • $\begingroup$ @G.Smith But there's obviously no way that a wave could provide a single quantum of energy to an atom. High-frequency light at low intensity would take a long time to charge up an atom. All the energy has to come from the light, it can't be that a few atoms are mostly charged up and just need a little push. So a wave just can't do it. It has to be big packets of energy that show up in one place. But I don't know the equations. Done right, it would be QM, correct? $\endgroup$ – J Thomas Apr 14 at 16:48
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Classical wave theory from Maxwell's Equations implies a rate of electro magnetic energy entering through the surface of a sphere at a rate much slower than is found in studying the photoelectric effect. About 10 minutes to launch an electron to observed velocities vs near instantaneous take off. Compare the surface integral of the Poynting Vector over the classic electron radius to observations. This might be an example of the failure of a wave theory to explain how photons propagate through space. It literally at the boundary of a particle process though.

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    $\begingroup$ Not to mention there are no physical descriptions of what a light wave is. It can’t be described unless you’re talking individual photon Particles. $\endgroup$ – Bill Alsept Apr 13 at 22:07

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