TIR (total internal reflection) in terms of quantum world

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Discussion Overview

The discussion centers on the phenomenon of total internal reflection (TIR) and its explanation within the context of quantum mechanics. Participants explore the relationship between classical and quantum descriptions of light behavior at the interface of different media, particularly when the angle of incidence exceeds the critical angle.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions how TIR occurs in the quantum realm, particularly regarding the behavior of electrons at the interface when light is incident at an angle greater than the critical angle.
  • Another participant suggests that quantum mechanics is not necessary to explain macroscopic phenomena like TIR, emphasizing that the phase conditions of secondary sources determine light propagation.
  • It is proposed that while individual atoms emit photons in all directions with equal probability, the synchronization of these emissions at the time of interaction with incoming light leads to the observed directionality of emitted light.
  • The concept of the evanescent wave is introduced, noting that the electromagnetic field does not completely vanish beyond the surface during TIR, allowing for some penetration into the medium.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of quantum mechanics for explaining TIR, with some advocating for a classical perspective while others seek a quantum explanation. The discussion remains unresolved regarding the role of quantum effects in this phenomenon.

Contextual Notes

The discussion highlights the complexity of reconciling classical and quantum descriptions of light behavior, with assumptions about atomic behavior and the nature of light propagation remaining implicit and not fully explored.

Pritamstar
how total internal reflection of light takes place in terms of quantum world?
 
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Pritamstar said:
how total internal reflection of light takes place in terms of quantum world?
What are your thoughts on this? What is the context of your question? Is this for homework?
 
its not homework, actually i was thinking when a light beam falls at the interface of a medium with angle more than critical it undergoes TIR But in quantum world the electrons present on the edge would absorb it then when they release it how do they know they have to release the photon in inward direction..
 
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Pritamstar said:
its not homework, actually i was thinking when a light beam falls at the interface of a medium with angle more than critical it undergoes TIR But in quantum world the electrons present on the edge would absorb it then when they release it how do they know they have to release the photon in inward direction..
The same as the other macroscopic EM phenomena such as reflection and refraction, you don't need to resort to quantum mechanics to explain them. The macroscopic effect of light propagation is determined by the phase condition of the various secondary sources across the beam path. In this case the atoms near the surface on which the light impinges.
Microscopically there shouldn't be any preferred direction to which the atoms emit photons. Individually, each atoms emit with the same probability in any direction. However, depending on how synchronized they were at the time of interaction with the incoming light (i.e. the incident angle), the net effect is that the emitted light has certain directionality. Also, the EM field beyond the surface in the case of TIR does not completely vanish, a certain amount can still penetrate up to some depth which is called the evanescent wave.
 
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