Question

When unpolarised light beam is incident from air onto glass $(n=1.5)$ at the polarising angle.

• A. Reflected beam is polarised $100$ percent
• B. Reflected and refracted beams are partially polarised
• C. The reason for (a) is that almost all the light is reflected
• D. All of the above

Answer 1

The correct option is A Reflected beam is polarised $100$ percent

A

When the incident light crosses the interface the light is absorbed temporarily by the atoms in the second medium. Electrons in these atoms oscillate back any forth in the direction of the electric field vectors in the refracted ray, perpendicular to the direction, the refracted ray is travelling.

The light is remitted by the atoms to form both the reflected and refracted rays. The electric field vector in the light match the directions the electrons were oscillating, and they must've be perpendicular to the direction of propagation of the wave. When the lights comes in at the Brewster angle the reflected wave has no electric field vectors parallel to the refracted ray, because the electrons Di not oscillate along that direction. The reflected wave also have no electric field vectors parallel to the reflected ray, because that's the direction of propagation of the wave. The only direction possible is perpendicular to the plane of the picture. So, the reflected ray is linearly polarized.