There is a crystal through which when light passes through it gets polarised...
Polarization
Light waves from the sun, or even from an artificial light source such as a light bulb, vibrate and radiate outward in all directions. Whether the light is transmitted, reflected, scattered or refracted, when its vibrations are aligned into one or more planes of direction, the light is said to be polarized. Polarization can occur either naturally or artificially. You can see an example of natural polarization every time you look at a lake. The reflected glare off the surface is the light that does not make it through the "filter" of the water, and is the reason why you often cannot see anything below the surface, even when the water is very clear.
When ordinary light passes through a tourmaline crystal, only those vibrations that are parallel to the crystallographic axis AB, pass through. Thus the emergent light has its vibrations confined to a single plane only. Now we will define certain relevant terms.
The process of transforming unpolarized light into polarized light is known as polarization of light.
Depending on the orientation of the electric field, polarized light can be divided into three types-
Linear polarization- When an ordinary(unpolarized)light is reflected from a polished surface or transmission through certain materials, the electric fields vector oscillates along a straight line in one plane, and the light is said to be linearly polarized.
Circular polarization- The electric field of light consists of two linear components that are perpendicular to each other, equal in amplitude, but have a phase difference of π/2. The resulting electric field rotates in a circle around the direction of propagation and, depending on the rotation direction, is called left- or right-hand circularly polarized light.
Elliptical polarization- The electric field of light describes an ellipse. This results from the combination of two linear components with differing amplitudes or a phase difference that is not π/2. This is the most general description of polarized light, and circular and linear polarized light can be viewed as special cases of elliptically polarized light.