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If a single photon strikes a glass slab of certain thickness, can we make prediction whether it would reflect or refract? On which factor the reflection or refraction of single photon through such a material depend?

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  • $\begingroup$ Neglecting atomic and solid state physics effects it's the same optical prediction that we get from Fresnel equations for the reflected intensity: en.wikipedia.org/wiki/Fresnel_equations. Having said that, one needs to be careful with "single photons" that interact with matter. Light inside a piece of matter isn't properly described by free photon states and a complete naive description with quantum electrodynamics would be essentially impossible to carry out. We may as well stick to the classical and descriptions and we wouldn't have to remove all the atomic and solid state physics effects. $\endgroup$
    – CuriousOne
    Commented Jun 18, 2016 at 7:53

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Exactly this phenomenon is used in beam splitters. A beam splitter is normally designed to have a 50% chance of reflection and a 50% chance of reflection, while your glass block will (probably) not have equal reflection and transmission probabilities. However the basic principle is the same.

Incidentally there is a related question at What happens when a photon hits a beamsplitter? and you may be interested to read the answers to that question.

The answer is that when the photon reaches your glass slab it will form a superposition of the reflected and transmitted states. So the photon is both reflected and transmitted. If we interact with the system to perform a measurement we will collapse the superposition and we'll find out whether the photon was reflected or transmitted. However there is no way to tell in advance what the result will be. The best we can do is calculate the probabilities that the measurement will find the photon in the two states.

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  • $\begingroup$ I was wondering the thickness of slab could account a little....doesn't it? $\endgroup$
    – Lamichhane88
    Commented Aug 8, 2016 at 14:59
  • $\begingroup$ @Lamichhane88 According to the second QED lecture by Feynman, the thickness determines chance of reflection. $\endgroup$
    – Cees Timmerman
    Commented Jul 6, 2017 at 18:29

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