Question

Polarization, namely the filtering of non-polarized light waves (the direction of the vibrations of the electric field randomly) into one axis can occur by absorption, reflection, scattering, briefly describing the differences in the three, and examples

Answer 1

Ans:

A light wave that is vibrating in more than one plane is referred to as unpolarized light. Polarized light waves are light waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as polarization. Polarization can occur by absorption, reflection, scattering and refraction.

Polarization by reflection:

Polarization can occur when light reflect off of nonmetallic surfaces. The extent to which polarization occurs is dependent upon the angle at which the light approaches the surface. Nonmetallic surfaces such as asphalt roadways, snowfields and water reflect light such that there is a large concentration of vibrations in a plane parallel to the reflecting surface. A person viewing objects by means of light reflected off of nonmetallic surfaces will often perceive a glare if the extent of polarization is large.

Example: Fishermen are familiar with the glare since it prevents them from seeing fish that lie below the water. Light reflected off a lake is partially polarized in a direction parallel to the water's surface.

Polarization by scattering:

Polarization also occurs when light is scattered while traveling through a medium.The absorption and reemission of light waves causes the light to be scattered about the medium.This scattered light is partially polarized. Polarization by scattering is observed as light passes through our atmosphere. The scattered light often produces a glare in the skies.

Example:

Photographers know that the partial polarization of scattered light leads to photographs characterized by a washed-out sky. They correct this problem by the use of a Polaroid filter

.Polarization by Absorption:

A number of crystalline materials absorb more light in one incident plane than another, so that light progressing through the material become more and more polarized as they proceed. This anisotropy in absorption is called dichroism. Commercially these materials are used as polarizers.When unpolarized light is transmitted through a Polaroid filter, it emerges with one-half the intensity and with vibrations in a single plane; it emerges as polarized light. The alignment of the molecules of the material gives the filter a polarization axis. Any vibrations that are perpendicular to the polarization axis are blocked by the filter.

Example:

PPolaroid filters are used to perform stress analysis tests on transparent plastics. As light passes through a plastic, each color of visible light is polarized with its own orientation.