Answer to Question #164099 in Optics for Xavier

Question

How will you demonstrate that a beam of light is completely polarized?

Answer 1

According to the findings from the research done by Brewster in optics, it is explained that when a beam of light which is unpolarized undergoes reflection from a transparent medium, the reflected light is entirely plane polarized at an angle of polarization.

Where the angle of polarization lies on a certain angle of incidence ($i$ )

From the figure below and Snell's law: $\eta =\frac{sin\:i}{sin\:r}$ where $\eta$ is the refractive index, $i$ is the angle of incidence and $r$ is the angle of refraction. The angle of incidence can be obtained where the reflected light is plane polarized completely.

The unpolarized beam of light will be completely polarized when it is reflected from the boundary of refraction of light as shown on the above figure. The fact that the beam of light strikes an interface so that the $90^{\circ }$ angle between the reflected and refracted beams is a clear indication that the beam of light is completely polarized.