Question regarding the three polarizer paradox

  • Context: Undergrad 
  • Thread starter Thread starter SeanHannity
  • Start date Start date
  • Tags Tags
    Paradox Polarizer
Click For Summary

Discussion Overview

The discussion revolves around the three polarizer paradox and whether the effects observed in this experiment can be replicated using materials other than traditional polarizers. Participants explore the nature of polarizers, the implications of classical versus quantum mechanics, and the definitions surrounding the term "paradox."

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question whether the three polarizer experiment's results can be achieved with non-polarizing materials or different types of filters.
  • Others clarify that a polarizer's function is independent of the material, focusing instead on effective parameters and types of polarizers.
  • There is a discussion on the nature of the paradox, with some arguing it is not a true paradox but rather a counterintuitive result.
  • Several participants emphasize the quantum mechanical aspects of the experiment, while others argue that classical electromagnetism can also explain the results.
  • Some participants note that classical predictions align with quantum results, suggesting compatibility rather than contradiction.
  • Concerns are raised about the terminology used in describing the effects of polarizers, particularly the notion of "subtracting light" versus changing polarization.
  • References to Dirac's work are made, highlighting the historical context and interpretations of the experiment.

Areas of Agreement / Disagreement

Participants express differing views on whether the three polarizer experiment constitutes a paradox and whether classical mechanics can fully explain the observed phenomena. There is no consensus on the implications of using different materials or the definitions surrounding polarizers.

Contextual Notes

Some participants point out limitations in understanding the experiment, such as the dependence on definitions of polarization and the nuances of classical versus quantum interpretations. The discussion remains open-ended regarding the implications of using various materials in the experiment.

  • #31
anorlunda said:
My bad. I thought it was a QM-only thing.
You don't use QM to describe what happens in your VP VHF boat antenna. RF electromagnetism make so much more sense when people want some 'understanding'. You can 'feel' the currents flowing and the result of tilting an antenna.
 
  • Like
Likes   Reactions: anorlunda and vanhees71
Science news on Phys.org
  • #32
Ibix said:
I think a better picture is to think of the polaroid as an array of antennae that are driven by the incident wave to emit a new wave.
I had never heard that before. Very Huygens-like.
 
  • #33
Dale said:
I had never heard that before. Very Huygens-like.
Really? I thought it was a fairly standard explanation of how wire grid (and similar) polarisers work, an anisotropic relative of the usual explanation of why EM waves don't penetrate metals. The charges can't move very far across the grid.
 
  • #34
Usually the treatment is using "macroscopic electrodynamics", i.e., Maxwell's equations for ##\vec{E}##, ##\vec{B}## and ##\vec{D}## and ##\vec{H}## with consitutive equations motivated from linear-response theory (in very advanced special treatments the latter derived from quantum many-body theory). Then of course the microscopic picture that the electromagnetic field is due to the superposition of the incoming (external) em. field and the em. field from the motion of the charges in the material.

For a treatment in the latter spirit see the very nice textbook by Schwartz:

M. Schwartz, Principles of Electrodynamics, Dover Publications (1972)

It's a bit like a book with the didactical intentions of Purcell in the Berkeley physics book done right, though there are still some rough edges in there (e.g., the use of the concept of "relativistic mass").
 
  • Like
Likes   Reactions: Ibix
  • #35
vanhees71 said:
Argh! That's also a paradox now. Well, I've to reformulate next week's problem set for my students to make them solve a paradox rather than some projection operator applications ;-)).
Well, it's always more fun to solve a straightforward problem when it is presented as a "paradox". At least to me. :smile:
 
  • #36
Demystifier said:
Well, it's always more fun to solve a straightforward problem when it is presented as a "paradox". At least to me. :smile:
That's probably true. It can bring out your argumentative side and makes you more determined to disprove the paradox. Everyone loves a Devil's Advocate.
 
  • Like
Likes   Reactions: Demystifier
  • #37
anorlunda said:
Can it be explained classically?

Yes, using Jones vectors. The 3-polarizer setup is a very useful (and classical) way to demonstrate the behavior of spin-polarized atoms in magnetic fields. The Pauli spin matrices serve double-duty as Hermitian polarization operators.

The central concept common to both is 'change of basis states'.
 
  • Like
Likes   Reactions: vanhees71 and anorlunda

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
Replies
11
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 43 ·
2
Replies
43
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 52 ·
2
Replies
52
Views
7K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 19 ·
Replies
19
Views
994
  • · Replies 8 ·
Replies
8
Views
3K