Polarization by Reflection

                                                      Polarization by Reflection

The simplest method of polarization of light is called polarization of reflection. Malus discovered in 1809 that polarized light gets linearly polarized upon reflection. When a beam of white light is incident at a certain angle on the surface of a glass plate. 

Explanation

Consider an unpolarized beam falls on a surface plate. The E vectors are resolved into two component. one component of E is perpendicular to the plane of incidence or plane. While the other component of E is parallel to this plane.

It is found experimentally that reflected and the refracted beam are at right angle.

`\theta_{p}-\theta_{r}=90`

from Snell's law

`n_{1}\sin\theta_{p}=n_{2}\sin\theta_{r}`

combining this two equations

`n_{1}\sin\theta_{p}=n_{2}\sin(90^{\circ}-\theta_{p})`

`n_{1}\sin\theta_{p}=n_{2}[sin90^{\circ}\cos\theta_{p}-\cos90\sin\theta_{p}]`

`n_{1}\sin\theta_{p}=n_{2}\cos\theta_{p}`

`\tan\theta_{p}=\frac{n_{2}}{n_{1}}`

This equation is called Brewster law.