Reflection of a plane mirror and phase shift

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Homework Help Overview

The discussion revolves around the behavior of linearly polarized light when it reflects off a plane mirror with a higher index of refraction. The original poster is uncertain about whether a 180-degree phase shift during reflection affects the direction of polarization.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the effects of phase shifts on polarization direction, with one questioning the implications of the mirror's properties on the polarization state. Another participant discusses the differences in reflection coefficients for various polarization states and how this might affect the resultant polarization.

Discussion Status

Some guidance has been provided regarding the relationship between phase shifts and polarization, particularly in the context of Fresnel's equations. The original poster seeks further clarification and references, indicating an ongoing exploration of the topic.

Contextual Notes

There is mention of complexities introduced by the material of the mirror and the angle of incidence, which may affect the polarization state of the reflected light. The original poster references a potential analogy to a half-wave plate, indicating a need for deeper understanding of these concepts.

Niles
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Homework Statement


Hi

I think I have confused myself: If I have a linearly polarized beam incident on a plane mirror with higher index, will the 180-degree phase shift change the direction of the polarization? Say, from lying in the 1st-3rd quadrant to lying in the 2nd-4th quadrant? Personally I would say no, since the mirror has no way to "tell" what the 1st-3rd quadrant actually is. But I am not 100% sure my argument works.


Niles.
 
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The pi phase change during reflection does not change the direction of polarization.
But: the coefficient of reflection is different for waves polarized in the plane of incidence and for those, perpendicular to the plane(TM and TE mode waves).
If the incident wave has both parallel and perpendicular components, the ratio of the components will change upon reflection, and so does the direction of polarization.
When the mirror is from metal, the situation is even more complicated at non-normal incidence, as not only the amplitudes of the wave components change but their phases, too. Therefore the reflected light becomes elliptically polarized.

ehild
 
Hi

Thanks, do you have a reference where these things are explained?Niles.
 
It is any handbook of Optics, O.S. Heavens, Optical Properties of Thin Films, Academic Press, 1955, for example. Google "Fresnel coefficients", "polarization of light by reflection".

ehild
 
Hi again

Ok, so from Fresnel's equations I see that the component perpendicular to the plane of incidence gets an additional phase of 180 degrees upon reflection. That means that there is a net relative change between the components of 180 degrees upon reflection. But this is practically just what a half-wave plate does?

Where am I wrong here?
 
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