Intensity for circular polarised light through linear polariser

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Discussion Overview

The discussion revolves around the behavior of circularly polarized light as it passes through linear polarizers, specifically examining the intensity changes and polarization states involved in different configurations of optical elements.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the intensity of circularly polarized light changes when it passes through a linear polarizer, proposing two different configurations for analysis.
  • Another participant asserts that the second polarizer reduces the intensity of circularly polarized light by half.
  • A third participant adds that a plane polarizer treats circularly polarized light similarly to unpolarized light, implying that it does not retain the circular polarization after passing through.
  • A later reply suggests that the quarter-wave plate would not alter the polarization in the first configuration, questioning its utility in that scenario.

Areas of Agreement / Disagreement

Participants express differing views on the effects of the quarter-wave plate and the outcomes of the two proposed configurations, indicating that the discussion remains unresolved regarding the effectiveness of the optical elements in each case.

Contextual Notes

There are assumptions regarding the behavior of light through polarizers and the specific effects of the quarter-wave plate that remain unexamined, as well as potential dependencies on the definitions of polarization states.

dalind
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Hi,

does the intensity change when circularly polarised light passes through a linear polariser?
I am thinking of a flow like this: natural light -> vertical linear polariser -> quarter wave plate -> horizontal linear polariser -> intensity?

After the first polariser, the intensity is 50%, the quarter wave plate changes the linear polarisation to circular. But does the horizontal linear polariser decrease the intensity again?

Edit: Another flow would be natural light -> 45° linear polariser -> quarter wave plate -> - 45° linear polariser -> intensity? Since I think the polarisation is not affected by the quarter wave plate if the light is polarised vertically, I think the first flow would result in a complete absorption of the light by the second polariser (Intensity 0), right?

Thank you.

Cheers,
dalind
 
Last edited:
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Yes, the second polariser cuts the intensity of the circular light in half.
 
Last edited:
... and makes it linearly polarized.
A plane polarizer treats circularly polarized light the same as it treats unpolarized light.
 
Okay, thanks. That's what I thought. And this only works for the second flow I described, for the first one the quarter-wave plate would not change the polarization and would therefore practically be useless, right?
 

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