Polarization of Light

What is Polarization?

Polarization, in Physics, is defined as a phenomenon caused due to the wave nature of electromagnetic radiation. Sunlight travels through the vacuum to reach the Earth, which is an example of an electromagnetic wave. These waves are called electromagnetic waves because they form when an electric field that interacts with a magnetic field. In this article, you will learn about two types of waves, transverse waves, and longitudinal waves. You will also learn about polarization and plane polarised light.

Transverse waves

Transverse waves are waves, i.e. movement of the particles in the wave is perpendicular to the direction of motion of the wave.

Example 1: ripples in water, when you throw a stone.

Example 2: the motion of sound waves through the air.

Longitudinal waves are when the particles of the medium travel in the direction of motion of the waves.

Light is the interaction of electric and magnetic fields travelling through space. The electric and magnetic vibrations of a light wave occur perpendicularly to each other. The electric field moves in one direction and magnetic in another though always perpendicularly. So, we have one plane occupied by an electric field, the magnetic field perpendicular to it, and the direction of travel which is perpendicular to both. These electric and magnetic vibrations can occur in numerous planes. A light wave that is vibrating in more than one plane is known as unpolarized light. The light emitted by the sun, by a lamp or a tube light are all unpolarised light sources. As you can see in the image below, the direction of propagation is constant, but the planes on which the amplitude occurs is changing.

The image here shows its various types:

The other kind of wave is a polarized wave. Polarized waves are light waves in which the vibrations occur in a single plane. Plane polarized light consists of waves in which the direction of vibration is the same for all waves. In the image above, you can see that a Plane polarized light vibrates on only one plane. The process of transforming unpolarized light into the polarized light is known as polarization. The devices like the purple blocks you see are used for the polarization of light.

Types of Polarization

Following are the three types of polarization depending on the transverse and longitudinal wave motion:

• Linear polarization
• Circular polarization
• Elliptical polarization

Linear Polarization

In linear polarization, the electric field of light is limited to a single plane along the direction of propagation.

Circular Polarization

There are two linear components in the electric field of light that are perpendicular to each other such that their amplitudes are equal, but the phase difference is

Elliptical Polarization

The electric field of light follows an elliptical propagation. The amplitude and phase difference between the two linear components are not equal.

Methods Used in the Polarization of Light

There are a few methods used in the polarization of light:

• Polarization by Transmission
• Polarization by Reflection
• Polarization by Scattering
• Polarization by Refraction

Polarization Applications

Following are the applications of polarization:

• Polarization is used in sunglasses to reduce the glare.
• Polaroid filters are used in plastic industries for performing stress analysis tests.
• Three-dimensional movies are produced and shown with the help of polarization.
• Polarization is used for differentiating between transverse and longitudinal waves.
• Infrared spectroscopy uses polarization.
• It is used in seismology to study earthquakes.
• In Chemistry, the chirality of organic compounds is tested using polarization techniques. 

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