Phase shift of reflected light wave

[Zolo]

When a light wave move from a medium with lower refractive index to medium of higher refractive index, at the boundary, the reflected light wave will undergo a phase shift of ∏ rad.
Compared to the transmitted light, the reflected light lead by ∏ rad or lag by ∏ rad?

 

[Born2bwire]

When a light wave move from a medium with lower refractive index to medium of higher refractive index, at the boundary, the reflected light wave will undergo a phase shift of ∏ rad.
Compared to the transmitted light, the reflected light lead by ∏ rad or lag by ∏ rad?

That's not true. The phase shift depends upon the angle of the incident light, the polarization of the light, and the material properties. For example, if we have transverse magnetic polarized light that is incident normally to the surface and the materials are lossless dielectrics, then there is no phase shift between the reflected, transmitted and incident waves.

 

[Meir Achuz]

When a light wave move from a medium with lower refractive index to medium of higher refractive index, at the boundary, the reflected light wave will undergo a phase shift of ∏ rad.
Compared to the transmitted light, the reflected light lead by ∏ rad or lag by ∏ rad?

I assume you mean normal incidence. There will be a phase change of pi.
Lagging by pi is the same as leading by pi.