What is Polarization? – Definition, Types & Uses

Let’s start with the introduction of the definition of polarization. In this article, examples, uses, and types of polarization are discussed.

What is Polarization?

A light wave that vibrates in more than one plane is referred to as unpolarized light such as the light emitted by the sun, a lamp, or candle flame is unpolarized light. Such light waves consist of an electromagnetic wave that vibrates in a variety of directions. However, it is possible to transform unpolarized light into polarized light.

What is Polarization

Polarized light waves are the waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as polarization.


The phenomenon of restricting the vibration of light (electric field) in a particular direction (plane), perpendicular to the direction of wave motion is called polarization of light.

Polarizer or Polaroid

A thin plastic-like sheet, consisting of long-chain molecules aligned in a particular direction.

Plane of Polarization

If an unpolarized light wave is an incident on such a Polaroid then the light wave gets linearly polarized with the electric vector oscillating along the direction perpendicular to the aligned molecules. The plane in which the vibrations of polarized light are confined is the plane of vibration/polarization.


Polarization by a Polaroid filter

These Polaroid filters are made of a special material that is capable of blocking one of the two planes of vibration of, electromagnetic waves that are filtered out one-half of the vibrations upon the transmission of the light through the filter. When unpolarized light is transmitted through a Polaroid filter, it emerges with one-half the intensity and with vibrations in a single plane, as polarized light.

These filters are able to polarize light because of the chemical composition of the filter material. The filter has long-chain molecules that are aligned within the filter in the same direction. A Polaroid filter with its long-chain molecules aligned horizontally will have a polarization axis aligned vertically.

Such a filter blocks all horizontal vibrations and allows only the vertically will have a polarization axis aligned horizontally; it blocks all vertical vibrations and allows only the horizontal vibrations to be transmitted.


Polarization of Reflection

Unpolarized light can also undergo polarization by reflection off non-metallic surfaces such as asphalt roadways, snowfields, and water. They reflect light so that there is a large concentration of vibrations in a plane parallel to the reflecting surface.

Someone viewing objects by light reflected off non-metallic surfaces will often perceive a glare if the extent of polarization is large. Fishermen are familiar with this glare since it prevents them from seeing fish that lies below the water.

Brewster’s Law

If the angle of incidence of which the reflected light is completely plane polarized is called polarizing angle or Brewster’s angle.

Brewster’s Law

When an unpolarized light incident at a polarizing angle, ip  on an interface separating air from a medium of refractive index, then the reflected light is fully polarized if

  μ = tan ip

According to Snell’s law

μ = sin i/sin r

Basically reflected ray should be perpendicular to refracted ray. In that case only i=ip & r=90-ip.

  i = ip

     r = 90 – ip

    μ = sin ip/sin(90-ip)

    μ = tan ip


Polarization by Refraction

Polarization also occurs by the refraction of light in a plane perpendicular to the surface. The polarization of refracted light is often demonstrated by Nicol’s prism or Iceland Spar, a rare form of mineral calcite.

It refracts incident light into two different paths that are light splits into two beams upon entering the crystal. Subsequently, if an object is viewed by looking through an Iceland Spar crystal, two images are seen. These two images are the result of the double refraction of light. Both refracted light beams are polarized.

Polarization by Scattering

It is observed as light passes through our atmosphere. The scattered light often produces glare in the skies. Photographers know that this partial polarization of scattered light leads to photographs characterized by a washed-out sky. This problem is corrected by the user of the Polaroid filter.

When the filter is rotated, the partially polarized light is blocked and the glare is reduced. The photographic secret of capturing a clear blue sky as the backdrop of a beautiful foreground lies in the physics of polarization and Polaroid filters.


Application of Polarization of light in glare-reducing sunglasses and in the entertainment industry to produce and show 3-D movies.


Uses of Polarized light and Polaroid

  • Polaroids are useful in 3-D motion particles that are holography.
  • Polaroid s are also used to avoid the glare of light.
  • The objectives of the microscope are fitted with polaroids to avoid glare in observing minute particles.
  • Polarization is used to study asymmetric in crystals and molecules using the phenomenon of optical activity.


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