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I want to ask that whether there is any phase change during reflection of a P-polarised wave? I know that for a S- Polarised wave there is a phase change of 180° when wave travels from rarer to denser medium.

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Yes there is. Actually what you are referring to, that there is no phase change of a P polarized wave, that only happens when there is a glancing angle, so beyond the Brewster angle, the phase change is 0.

But in case of a normal incidence, like perpendicular, the P polarized wave will have a phase change that is non 0 (when traveling from rarer to denser medium).

Polarized light with its electric field along the plane of incidence is P polarized.

When the electric field is normal to the plane of incidence, it is S polarized.

It is very important to say that you are talking about specular reflection. In this kind of reflection, the relative phases and angles of photons is kept, so a mirror image is built. If you were talking about diffuse reflection, in that case, there is no sense talking about the phase and the angle of the wave (at least not how it is kept relatively), because the angle of reflection is random.

So in your case, specular reflection, any light striking at the Brewster angle, where the reflection coefficient for P polarized light is 0, will only be reflected with the S polarization remaining.

In the case of normal incidence angle, there is no difference between the S and P polarized light, both will be reflected with a π phase-shift.

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  • $\begingroup$ @ProfRob thank you so much, I edited. $\endgroup$ Commented Apr 25, 2021 at 16:39

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