Polarization by Reflection, Brewster's Angle

Light becomes partially linearly polarized upon reflection. If the angle of incidence equals Brewster’s angle (which is defined by the condition that the reflected and transmitted beams are perpendicular), the reflected light is fully linearly polarized with the polarization direction perpendicular to the plane of incidence.

This can be demonstrated by illuminating the interface with linearly polarized light. If the polarization is perpendicular to the plane of incidence, all light is reflected. If the polarization lies in the plane of incidence, no light is reflected.

Polarizing filter placed in the beam path with its transmission axis oriented such that the resulting polarization direction is perpendicular to the plane of incidence.

Polarizing filter placed in the beam path with its transmission axis oriented such that the resulting polarization direction lies in the plane of incidence.

Incidence from an optically less dense medium at Brewster’s angle. The reflected and transmitted beams are perpendicular.

Incidence from an optically less dense medium at Brewster’s angle with a polarizing filter inserted. The polarization direction is perpendicular to the plane of incidence.

Incidence from an optically less dense medium at Brewster’s angle. The polarization direction lies in the plane of incidence. No light is reflected!

Incidence from an optically denser medium at Brewster’s angle. The reflected and transmitted beams are perpendicular.

Incidence from an optically denser medium at Brewster’s angle. The polarization direction is perpendicular to the plane of incidence.

Incidence from an optically denser medium at Brewster’s angle. The polarization direction lies in the plane of incidence. No light is reflected!