Under what circumstances is the phase of light changed by reflection? Is the phase related to polarization?

Polarization is a phenomena generated by the wave nature of electromagnetic radiation, according to physics.

Only when the polarised beam encounters a medium with a higher refracting index does it undergo phase change. When an unpolarised beam of light passes through a material, it is partially reflected and partially refracted. This refracted and reflected beam is also polarized to some extent. The horizontally polarised light beam is reflected by the medium's surface.

The phase of the resultant beam changes if the light beam reaches a medium with a higher refracting index; otherwise, there is no phase shift. Because the phase of the wave changes with place and time, while polarization does not, phase is unrelated to polarization.

Therefore, polarization has no bearing on phase change.