Why does light become polarized at Brewster's angle?

[Wrichik Basu]

Quoting Resnick and Halliday's Fundamentals of Physics (page 912) on polarization by reflection:

In general, the reflected light also has both components (the parallel and perpendicular components of Electric Field) but with unequal magnitudes.This means that the reflected light is partially polarized—the electric fields oscillating along one direction have greater amplitudes than those oscillating along other directions.

It is also known that when light is incident at the interface at a particular angle θ_b, the Brewster angle, the reflected light is completely plane polarized.

Why does light get polarized when it gets reflected? What interaction on the atomic scale results in a polarised reflected light?

How can this be interpreted quantum mechanically?

I searched on Google, got this answer, but it's not satisfactory. Can anyone provide a better answer or source?

 

[Charles Link]

This is a bulk property of the material with index $n$ and not about atomic properties. The index $n$ is assumed to be independent of polarization. The Fresnel relations are derived simply by employing the Maxwellian boundary conditions. See https://www.brown.edu/research/labs....labs.mittleman/files/uploads/lecture13_0.pdf