Brewster’s angle, also known as the polarization angle, is the specific angle of incidence at which light becomes polarized upon reflection.

When light strikes a surface, it can undergo three possible outcomes: it can be reflected, refracted, or absorbed. Among these, reflected light can become polarized in a particular direction. At Brewster’s angle, the light that is reflected is polarized perpendicular to the plane of incidence. This unique property results in the reflected light being completely polarized, with no component of light reflected in the plane of incidence.

The Brewster’s angle can be calculated using the formula:

In this equation, $\theta_B$ represents Brewster’s angle, $n_1$ denotes the refractive index of the medium in which the incident light travels, and $n_2$ is the refractive index of the medium in which the reflected light propagates. The value of Brewster’s angle is thus dependent on the refractive indices of the two interacting media.

Brewster’s angle has numerous applications in optics. It is utilized in polarizing filters, anti-reflection coatings, and laser cavities. Polarizing filters are designed to block light that is polarized in a specific direction, while anti-reflection coatings minimize unwanted reflections on surfaces. Additionally, laser cavities often incorporate Brewster’s windows, which are positioned at Brewster’s angle to enable laser light to pass through without being reflected back.