Is the polarization of electromagnetic waves definite or in superposition?

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Discussion Overview

The discussion centers around the nature of polarization in electromagnetic waves, particularly whether it is definite or exists in a state of superposition. Participants explore the implications of classical and quantum mechanical perspectives on polarization, referencing Maxwell's equations and quantum field theory.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question whether classical electromagnetic waves have definite polarization when emitted from the sun or if they exist in superposition until measurement, drawing parallels to quantum mechanics.
  • One participant asserts that natural sunlight is randomly polarized, indicating a classical superposition of orthogonal components, but clarifies that this is not the same as quantum superposition.
  • Another participant suggests that while classical fields have definite values at any instant, the chaotic nature of their oscillation leads to the perception of randomness in polarization.
  • Some participants argue that when transitioning to quantum field theory, the polarization becomes indeterminate, raising questions about the implications of using different mathematical frameworks.
  • There is a discussion about the necessity of using classical descriptions versus quantum descriptions when discussing light from the sun, with some advocating for a classical approach and others suggesting the relevance of quantum mechanics.
  • One participant emphasizes the importance of understanding classical mechanics and electrodynamics as a foundation for grasping quantum mechanics, recommending resources for further study.
  • A later reply challenges the framing of the discussion, suggesting that the approach taken may be misleading.

Areas of Agreement / Disagreement

Participants express differing views on whether polarization is definite or in superposition, with no consensus reached on the implications of classical versus quantum descriptions of electromagnetic waves.

Contextual Notes

Participants highlight the complexity of transitioning between classical and quantum descriptions, noting that assumptions about polarization may depend on the mathematical framework used. There is an acknowledgment of the need for a solid understanding of classical physics to engage with quantum concepts effectively.

fanieh
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Hi,

In Classical electromagnetic wave.. does it have definite polarization when the EM wave leaves the sun for example? Or is it in superposition and the polarization only exist after measurement just like in QM?

I don't understand the Maxwell Equation. Does Superposition in Maxwell Equation means the polarization is in superposition and doesn't have definite value before measurement?

Thank you.
 
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fanieh said:
Hi,

In Classical electromagnetic wave.. does it have definite polarization when the EM wave leaves the sun for example? Or is it in superposition and the polarization only exist after measurement just like in QM?

I don't understand the Maxwell Equation. Does Superposition in Maxwell Equation means the polarization is in superposition and doesn't have definite value before measurement?

Thank you.

Natural sunlight is randomly polarized, meaning that the electric and magnetic fields do not oscillate in any preferred direction. They are indeed a superposition of orthogonal components, as you say. However this is not a superposition in the quantum mechanical sense. It is a superposition in the classical sense of of the superposition of electric and magnetic fields. The field at any given instant does have a definite value and direction, but it is generally oscillating so wildly that as far as I know our equipment cannot distinguish the changes, and so we say that the light is unpolarized or randomly polarized.
 
Sturk200 said:
Natural sunlight is randomly polarized, meaning that the electric and magnetic fields do not oscillate in any preferred direction. They are indeed a superposition of orthogonal components, as you say. However this is not a superposition in the quantum mechanical sense. It is a superposition in the classical sense of of the superposition of electric and magnetic fields. The field at any given instant does have a definite value and direction, but it is generally oscillating so wildly that as far as I know our equipment cannot distinguish the changes, and so we say that the light is unpolarized or randomly polarized.

But if you will use quantum field theory and the electromagnetic field becomes photons.. the superposition is actual and the field at any given instant doesn't have any definite value.. so how can changing mathematical tool makes the polarization becomes indetermined in principle?
 
fanieh said:
But if you will use quantum field theory and the electromagnetic field becomes photons.. the superposition is actual and the field at any given instant doesn't have any definite value.. so how can changing mathematical tool makes the polarization becomes indetermined in principle?
But why would you do that if you want to talk about a classical electromagnetic wave?
 
Sturk200 said:
But why would you do that if you want to talk about a classical electromagnetic wave?

I mean.. when we want to talk about light coming from sun.. must we use the description of classical electromagnetic wave with random but deterministic polarization or photon with truly indeterministic polarization? What is the actual?
 
Without understanding classical mechanics and classical electrodynamics first, you haven't any chance to understand quantum mechanics and quantum field theory! So first, get a good understanding about classical physics! A good starting point are the Feynman Lectures. You find them online for free:

http://www.feynmanlectures.info/
 
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fanieh said:
But if you will use quantum field theory and the electromagnetic field becomes photons...
That's a very misleading way of thinking about what's going on here. Vanhees71's advice in #6 is good.
 

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