I'm aware that in Optics, the complex index-of-refraction $\eta = n+ik$ is used, which famously leads to the reflection property at an incident angle, i.e. Fresnel's law:
However, $k$ is the absorption (edit: extinction or attenuation) coefficient, indicating a loss of energy when the wave propagates through the medium. Fresnel's law refers to the reflection, so it is unclear to me why the absorption should have any effect on the reflected ray.
- So, why is it that $k$ plays a role in the reflection? (An argument using Maxwell's Equations would be perfect.)
- Has Fresnel's law (in particular, w.r.t. measuring the reflected ray), ever been validated by an experiment?