Skip to main content

Polarization Property of Light

 

 

Polarization is the property that indicates the direction of the vibrations of transverse waves. Transverse waves are waves that oscillate in the direction perpendicular to the propagation. Examples of transverse waves are electromagnetic waves, transverse sounds, and earthquake waves. Longitudinal waves oscillate in the same direction as the propagation. We can observe it in transverse waves as its polarization is perpendicular to the propagation.

We actually experience this phenomenon with light every day. As you know, light is an electromagnetic wave. It consists of electricity and magnetism. When we talk about the polarization of light, we have to look at the electric field waves, not the magnetic field.

There are three kinds of polarization.

1) Linear Polarization

 Linear polarization waves propagate toward the observed plane. The sum of the electric field E components reaches the observer, provided that it is perpendicular to the progression.

 


 2) Circular Polarization

In this type of polarization, the magnitude of the electric field is constant. However, we perceive it as a circular motion as it rotates at a constant speed in a plane perpendicular to the direction of the wave. A wave that rotates clockwise with a resultant electric field angular frequency w is called a right circular polarization, and counterclockwise rotation is called a left circular polarization.

3) Elliptical Polarization 

E waves traveling in an elliptical direction are formed by both rotation and change in magnitude. Here, too, the phase difference between the E components is ± pi/2.


Is every light that comes into our eyes polarized? The answer is no. For example, the rays coming from the Sun, our source of life, or the lights coming out of incandescent lamps are not polarized, that is, they do not have a certain geometric direction, they emit light in all directions, that is, we cannot say that they are polarized at a certain angle. However, we can polarize the light emanating from these light sources to have the direction we want by using the methods of Selective Absorption Polarization, Reflection Polarization, and Birefringence and Polarization.

Polarization with Selective Absorption: With the help of polarizers, it can be ensured that unpolarized light is transmitted by electromagnetic light in a certain direction, and unwanted directions are prevented.

Polarization by Reflection: The electric field of the light incident on the transparent surface accelerates the electrons on the surface and causes these electrons to radiate. Thus, two waves are formed, reflected, and refracted. If we examine the wave parallel to the plane of reflection, we observe that the electrons accelerated by this component of the incident light beam move perpendicular to the reflected wave. A very small part of the incident wave is absorbed by the electrons, so the reflection of this component of the incident wave is quite strong. Since the electrons accelerated by the second component move parallel to the reflected wave, the electrons absorb most of the incident wave and the reflection is weak. In polarization by reflection, if an unpolarized light beam is parallel or perpendicular to the plane of reflection, the reflected light is unpolarized. If the incident wave has other angles of incidence, I mean not perpendicular or parallel, the reflected and refracted light beams are partially polarized, that is, the electric field vectors have two components. But if the angle between the reflected and refracted light is 90 degrees, the reflected light has only the component of the electric field vector parallel to the plane of reflection. This component creates a strong reflection. The angle of incidence of light in this case has a special name and is called the Brewster angle(​θB).

 

Polarization with Birefringence: The last method is to create polarization with the help of crystal. Crystals are to make light into two beams, that is, they have birefringent properties. Both parts of the split light become polarized. A ray polarized perpendicular to the plane of incidence is called a normal ray, and a ray polarized parallel to a parallel is called an extra-normal ray. Thin sheets of tourmaline crystal absorb one of these rays and pass the other. Thus, a polarized beam is obtained. In birefringent crystals, there is a direction where the two beams meet, and this is called the "optical axis".




Reference

https://acikders.ankara.edu.tr/pluginfile.php/98722/mod_resource/content/1/week-6.pdf

P. M. Fishbane, et al. Temel Fizik. Yayınevi: Arkadaş Yayınevi.

Labels:

Comments

Post a Comment

Popular posts from this blog

Statement of Bell's Inequality

 One of the most important applications of quantum mechanics is Bell's inequality. In 1965, John Stewart Bell actually thought that Einstein might be right and tried to prove it, but proved that quantum logic violated classical logic. It was a revolutionary discovery. Let's look at its mathematically simple explanation. To create the analogy, let's first write a classical inequality.   This inequality above is a classic expression. The quantum analogy of this expression represents the Bell inequality. With just one difference. Bell's inequality shows that the above equation is violated. Expressing Bell's inequality by skipping some complicated mathematical intermediates; While there is no such situation in the classical world that will violate the inequality we mentioned at the beginning, it is difficult to find a situation that does not violate this inequality in the quantum world. Reference https://www.youtube.com/watch?v=lMyWl6Pq904 https://slideplay...
1 comment
Read more

Bloch Sphere – Geometric Representation of Quantum State

    It is very difficult to visualize quantum states before our eyes. The Bloch sphere represents quantum state functions quite well. The Bloch sphere is named after physicist Felix Bloch. As you can see in the Bloch sphere figure below, it geometrically shows the pure states of two-level quantum mechanical systems. The poles of the Bloch sphere consist of bits |0⟩ and |1⟩. Classically, the point on the sphere indicates either 0 or 1. However, from a quantum mechanics point of view, quantum bits contain possibilities to be found on the entire surface of the sphere. Traditionally, the z-axis represents the |0⟩ qubit, and the z-axis the |1⟩ qubit. When the wave function in superposition is measured, the state function collapses to one of the two poles no matter where it is on the sphere. The probability of collapsing into either pole depends on which pole the vector representing the qubit is closest to. The angle θ that the vector makes with the z-axis determines this probabilit...
1 comment
Read more

Let's Define Quantum Programming

    Along with the strange discoveries of quantum physics, one of these ideas for how we could use it is quantum computers. Work on quantum computers, which is a pretty good idea, started small and became what it is today. Now we had to take one more step and do quantum programming. The first studies on this process were made in the early 2000s. However, these studies were more theoretical. This was because quantum computers were not yet technologically ready. Finally, with the serious development of quantum computers (of course, we are still not at the desired point) we started to create our quantum algorithms. Today, we can do these algorithms on IBM Quantum Experience, Microsoft Azure Quantum, DWave Leap Cloud, or with quantum development kits. With these platforms, most of which are open source, we can create our quantum algorithms with the Python language, which we use classically and which is the most common programming language. The fact that such platforms are open sou...
2 comments
Read more