Constant frequency of light and connection to QM

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Discussion Overview

The discussion centers around the behavior of light's frequency during refraction, specifically why it remains constant despite changes in velocity and wavelength in different media. Participants explore connections to quantum mechanics (QM) and seek a clearer explanation than provided in a textbook.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the electric field must remain continuous across the boundary of different media, implying that a change in frequency would create a discontinuity.
  • Another participant clarifies that while velocity and wavelength of light change in different media, the frequency remains constant.
  • A further explanation is proposed using an analogy of waves on ropes of different mass per unit length, indicating that the number of wave peaks must remain consistent across the boundary.

Areas of Agreement / Disagreement

Participants generally agree that the frequency of light does not change during refraction, but there are varying explanations and analogies presented, indicating some level of debate over the clarity and completeness of these explanations.

Contextual Notes

The discussion reflects a reliance on specific textbook explanations that may not be universally accessible, leading to requests for alternative clarifications. There is also an exploration of potential deeper connections to quantum mechanics that remain speculative.

Who May Find This Useful

Readers interested in the principles of light behavior, refraction, and the relationship between classical and quantum physics may find this discussion relevant.

Medtner
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Could someone provide a good explanation as to why light's frequency doesn't change under refraction? The textbook I'm using gave us a two step derivation and I don't really feel like it did a proper job in explaining anything (it's Haliday).

Also, a slightly *crackpot* follow up question - does it have somewhat of a deeper connection to QM, and how photons don't change their velocity in different mediums?
 
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I think the most straightforward answer is, after all there has to be the same E field on both sides of the boundary. Imagine the E field oscillating with one frequency on one side, and with another frequency at the other. There would always be a constantly changing discontinuity.
 
Medtner said:
and how photons don't change their velocity in different mediums?
But they do... Velocity and wavelength change, but frequency stays the same (see post above by @rumborak ).
 
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Medtner said:
Could someone provide a good explanation as to why light's frequency doesn't change under refraction? The textbook I'm using gave us a two step derivation and I don't really feel like it did a proper job in explaining anything (it's Haliday).

As not all of us have that book available, maybe you could reproduce it's explanation so we would know where to start.

As a handwaving argument involving a different type of wave, think of a rope that is attached to a second rope with different mass per unit length (hence different wave speed). If you start transverse waves in the first rope segment, as the peak amplitude entered the second segment it would induce a wave peak in that segment, one for one for each wave generated. So the number of waves per second has to be the same in both media.
 
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