^Brewster’s law

^Brewster’s law

Brewster discovered that when ordinary light is incident on the surface of a transparent medium the reflected light is partially plane polarized.

The extent of polarization depends on the angle of incidence. For a particular angle of incidence (called polarizing or Brewster angle (i_p or p)

1. the reflected light is found to be completely polarized with its vibrations perpendicular to the plane of incidence.

2. the reflected & transmitted rays are perpendicular to each other, as shown in figure.

3. μ = tan p                           [called Brewster law

At i = p Ray 1: Incident ray (unpolarised)

Ray 2: Reflected ray (completely polarised)

Ray 3: Refracted ray (partially polarised)

For a ray incident form air to glass

^aμ_g = 3/2, so p = tan^-1  3/2  ⇒ p = 56.3⁰

For a ray incident form air to water

^aμ_w = 4/3,  so p = tan^-1  4/3 ⇒  p = 53.1⁰