Question

Describe in detail with your own words two of the fundamental physical mechanisms with which polarized light is obtained.

Answer 1

Solution :

The polarized light can be obtained in the following ways:

1. By reflection: whenever ordinary light falls on a transparent media some part of it is reflected and some part of it refracted . When observed these both kind of parts so obtained are partially polarized. When angle of incidence is changed at some certain value of angle of incidence the reflected beam is perpendicular to the refracted beam at that situation the REFLECTED beam is completely polarized. The value of angle of incidence at that angle is known as BREWSTER angle. So we can obtain polarized light by reflection.

2. By double refraction : I an unpolarized light ray enters in calcite crystal it is divided into two parts one is known as ORDINARY RAY and other is Known as EXTRAORDINARY RAY. Both of these are linearly polarized. This property of such kind of crystal is known as double refraction. With the help of this property nicol prism is formed which convert unpolarized light ray into polarized light ray.

O RAY follows all laws of refraction and its speed is also same in all direction of crystal.

E RAY does not obey law of refraction so its speed varies in different directions of crystal.

Nicol prism is formed of calcite crystal which is cut into two parts and joined by a glue called CANADA balsam which helps is total internal reflection of E ray so both Ray's can be separated.