Polarized vs Unpolarized Light: Difference and Comparison

Polarization is a crucial concept in the world of physics. When it comes to optics, understanding and being able to manipulate polarization is one of the most important things.

Not only this, executing polarization control can be very useful for a number of imaging applications as well.

The enormous benefits of polarization, however, can only be reaped when this property of light is understood properly. Two important types of light under this property are – polarized and unpolarized light.

Key Takeaways

  1. Polarized light refers to light waves that vibrate in a single plane, while unpolarized light has randomly vibrating waves in multiple planes.
  2. Polarized light is used in sunglasses to reduce glare, while unpolarized light is used in general lighting and most electronic displays.
  3. Filters, crystals, or reflections can produce polarized light, while most natural and artificial light sources produce unpolarized light.

Polarized vs Unpolarized Light

Polarized light is a type of light wave where the vibrations of multiple light particles are restricted to only one plane, and the movement of the vibrations remains the same. Unpolarized light is those light waves where the light particles are scattered through vibrations on various planes.

Polarized vs Unpolarized Light
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Polarized light refers to those light waves in which the vibrations of light particles occur on a single plane. The process by which scattered light is restricted in such a way is known as polarization.

A variety of methods that can help polarize light waves are known to us. To name a few, some of the most widely known methods are polarization by transmission, reflection, refraction, and scattering.

Unpolarized light refers to those light waves in which the vibrations of light particles occur on more than one plane.

Some useful examples include light waves given off by the sun, a lamp lighting up a classroom, or a candle flame lighting up a dark room, halogen lighting, and even LED lights.

Comparison Table

Parameters of ComparisonPolarized LightUnpolarized Light
MeaningPolarized light refers to those light waves that are restricted to one plane only.Unpolarized light refers to those light waves that are scattered on more than one plane.
DirectionThe electric fields of polarized light oscillate in one direction only.The electric fields of unpolarized light oscillate in all directions.
NatureThe nature of polarized light is coherent.The nature of unpolarized light is incoherent.
IntensityThe nature of the polarizer used decides the intensity of polarized light.The nature of the source of light waves decides the intensity of unpolarized light.
ProductionPolarized light is produced by natural sources.Unpolarized light is produced when light waves go through the process of reflection, scattering or they simply travel through certain materials.
Phase differenceThe phase difference between the x and y components is always constant.The phase difference between the x and y components changes randomly.

What is Polarized Light?

Polarized light refers to those light waves in which the vibrations of the light particles are restricted to one plane only. In this, the direction of vibrations of waves is always the same.

This means that these light waves oscillate in only one direction. The polarizer used to convert the light waves decides the intensity of the polarized light.

This property of light is coherent. Moreover, the phase difference between the x and y components of the electric fields is always constant. Interestingly, those lights that are emitted by natural sources are always polarized.

The process by which unpolarized light is transformed into polarized light is called polarization. Some common methods include polarization by transmission, reflection, refraction, and scattering.

Polarized light was first discovered in 1669 by Erasmus Bartholin. He found that a double image is produced when objects are looked at through the crystals of the mineral Iceland spar in transmitted light.

He also discovered that calcite crystals somehow split light into two separate beams. Partially polarized light is reflected when light waves hit the surface of a dielectric material.

Some examples of these surfaces include still water, glass, highways, and even sheet plastics. The amount of polarized light reflected is defined by the optical properties of these surfaces.

What is Unpolarized Light?

Unpolarized light refers to those light waves in which the vibrations of light particles are scattered. This means that they occur on more than one plane.

In this, the electric fields oscillate in all directions and paths. The intensity of unpolarized light is decided by the nature of the source from which light is emitted.

Unpolarized light is known to be incoherent. It comes into existence when light waves pass through a process of reflection, scattering, or sometimes they simply pass through a material that unpolarized light.

Another important thing to remember about this concept is that the phase difference between the x and y components is random and changes unpredictably. Two distinct contrarily polarized currents combine to form one unpolarized light.

These two currents are such that one has half the amount of intensity when compared to the other. In a case where one of these currents is more impactful than the other, the light waves are referred to as partially polarized.

The characteristics of unpolarized light can be defined by the degree of polarization and the parameters of the polarized amount of light. Moreover, the polarized amount of light can be depicted by using a Jonas vector, that too of a polarized ellipse.

Main Differences Between Polarized and Unpolarized Light

  1. Polarized light is restricted to one plane, while unpolarized light has vibrations of light particles on more than one plane.
  2. The electric fields of polarized light oscillate in one direction only, while the electric fields of unpolarized light oscillate in all directions.
  3. The nature of polarized light is coherent, while that of unpolarized light is incoherent.
  4. The intensity of polarized light is decided by the nature of the polaroid, while that of unpolarized light is decided by the nature of its source.
  5. Polarized light comes from natural sources, while unpolarized light is reflected, scattered, or passed through some polarizing material.
  6. The phase difference between the x and y components of polarized light is always constant, while that of unpolarized light is unpredictable.
References
  1. https://www.osapublishing.org/abstract.cfm?uri=optica-4-1-64
  2. https://onlinelibrary.wiley.com/doi/abs/10.1002/prop.200310037

Last Updated : 18 August, 2023

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