1. The problem statement, all variables and given/known data 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. Best, Niles.