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Faraday Effect

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Faraday Rotation Effect

In 1945, an English scientist Michael Faraday FRS observed an effect while examining the effect of magnetic field on plane-polarized light waves. This effect was named after him as the Faraday Effect.

Faraday Effect is also known as the Faraday Rotation or the Magneto Optical Faraday Effect.

Faraday Effect causes the rotation of the plane of polarization (plane of vibration) of electromagnetic waves in particular substances in a magnetic field. 

This rotation varies proportionally with the projection of the magnetic field along the direction of the propagation of light.

This page discusses the observations of the Faraday effect, along with the Faraday Tyndall effect, and the Faraday effect in Layman's terms.

Faraday Effect

The Faraday effect is a physical magneto optical Faraday Effect MOFE) phenomenon.

The Faraday effect results in a polarization rotation that varies proportionally with the projection of the magnetic field along the direction of the light propagation. 

Do You Know?

Faraday Effect is a special case of gyro-electromagnetism. 

The gyro-electromagnetism is achieved only when the dielectric permittivity tensor is diagonal.

History of Faraday Effect

The Faraday effect discovered this effect in 1845. It was the first experimental evidence that light and electromagnetism relate to each other.

James Clerk Maxwell completed the theoretical basis of electromagnetic radiation (including visible light) in the 1860s and 1870s and Oliver Heaviside. 

For most of the part, this effect occurs in optically transparent dielectric materials like liquids under the influence of magnetic fields.

The left and right circularly polarized waves propagating at varying speeds lead to Faraday. 

Therefore, the property of propagation is known as circular birefringence. 

As a result, linear polarization can decompose into the superposition of two equal-amplitude circularly polarized components of opposite handedness and different phases. 

Therefore, the Faraday effect induces the effect of a relative phase shift that rotates the orientation of a wave's linear polarization.

Faraday Tyndall Effect

In the mid-1850s, Faraday spent an ample amount of time investigating the properties of light and matter. 

He made several hundred gold slides (thin enough to be transparent). These gold leaves were made by hammering the metal into very thin sheets (which were too thick for his purpose).

Also, he examined these thin sheets by shining light through them. However, Faraday used chemical means rather than mechanical.

For most of the part, his process involved washing the films of gold, which Faraday noticed produced a light/fainted ruby coloured fluid. 

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Further, he kept fluid samples in bottles to use for future experiments: shining a beam of light through the liquid. 

In his record, Faraday observes that the cone was well-defined in the fluid by the illuminated particles.

As a result of this experiment, Faraday is known as one of the first researchers into nanoscience and nanotechnology.

Thus he realized that this cone effect was made because the fluid contained suspended gold particles that were too small to be observed with the scientific apparatus of the time, moreover,  which scattered the light to the side. This is known as the Faraday Tyndall effect in colloids.

Inverse Faraday Effect

The orbit of an electron directed by a circularly polarized light beam is usually a solenoid with an axis parallel to its displaced initial velocity

As a rule, the motion of the electron produces a solenoidal current that generates a magnetic moment depending on the direction of the shifted initial velocity.

The average of magnetic moments per unit volume in a free electron gas gives a plain microscopic explanation for the theory of the inverse Faraday effect in metals.

Inverse Faraday Effect in Optics

In optics, the inverse Faraday effect is the inverse of the Faraday effect. 

A static magnetization M(0) induces by an external vibrating electrical field with the frequency ω.  Here,  ω can be obtained with a high-intensity laser pulse.

Here, the induced magnetization lies proportionally to the vector product of E and E*.

M (0) α E (ω) and E* (ω)

From this equation, we see that the circularly polarized light with the frequency should induce a magnetization along with the wave vector k. 

Because \[\overrightarrow{E}\] is in the vector product. Also, left- and right-handed polarization waves should induce magnetization of opposite signs.

Thus the induced magnetization is comparable to the saturated magnetization of the media.

Magneto Optical Faraday Effect

In physics, the Faraday effect, the Faraday rotation effect or the magneto optical Faraday effect are synonyms. To be simply speaking, the Faraday effect is the magneto optical phenomenon. 

A Faraday effect or the magneto optical phenomenon is the interaction between light and a medium. We refer to this phenomenon as the magneto optic Faraday Effect or MOFE.

Faraday Cage Effect

A Faraday cage a.k.a Faraday shield. It is a mesh or metallic enclosure that blocks electromagnetic fields. 

A Faraday shield is formed by a continuous covering of conductive material. 

In the case of a Faraday cage, a cage can be formed by a mesh of such conductive materials.

The Faraday cage works on the principle of an external electrical field that causes electrical charges to reside within the cage’s conducting material distributed so that they cancel the field's effect in the cage's interior.

Faraday cages protect sensitive electronic equipment from external RFI or the radio frequency interference.

They also consider devices that produce RFI, likewise radio transmitters, to prevent their radio waves from interfering with other nearby devices.

They also protect people and equipment against electric currents such as lightning strikes and electrostatic discharges.

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As a result, the enclosing cage conducts current around the outside of the enclosed space and nothing passes through the interior.

Faraday Effect in Layman's Terms

A dipole moment (usually just called "magnetic moment") is something an object has that creates it and behaves sort of like a compass needle. 

It's kind of a virtual compass needle enclosed within an object. 

When the thing is placed during a magnetic flux, the thing rotates until its dipole moment is lined up with the magnetic flux. 

The dipole moment of a compass needle itself is, of course, parallel to the length of the needle; so is that of a magnet. 

A flat loop of wire with a circulating current also features a dipole moment, which is perpendicular to the loop; so once you place the loop during a magnetic flux, it'll tend to rotate until it's perpendicular to the sector (because then the moment of a magnet are going to be parallel to the field).

FAQs on Faraday Effect

1. How Were Electromagnetism and Light Related?

Ans: Faraday observed that the plane of vibration of a beam of linearly polarized light incident on a piece of glass rotates on being subject to an applied magnetic field in its direction of propagation.

This examination was one of the primary indications that electromagnetism and light are related.

2. Why is Michael Faraday Important?

Ans: Faraday was one of the renowned scientists of the 19th century. His technical aspects led to the discovery of a number of new organic compounds. Among these, benzene was the first to liquefy a “permanent” gas. It was believed that benzene is incapable of liquefaction. 

Further, his major contribution was in the field of electromagnetism, i.e., electricity and magnetism.

Firstly, he generated an electric current from a magnetic field. 

Secondly, his work led him to the invention of the first electric motor and dynamo. 

Furthermore, he showcased the relationship of electricity with chemical bonding. 

This discovery of the effect of magnetism on light produced diamagnetism, the peculiar behavior of certain substances in strong magnetic fields. 

3. Describe a Magnetic Moment in Simple Words.

Ans: It is a basic law of nature that once you have an electrical current---that is, charged particles moving---a magnetic flux exerts a force on these particles.

So if you've got a current loop, then the magnetic flux exerts a force on every tiny little electron therein loop because it moves along, and once you add it all up, you get torque on the wire.

By an equivalent principle, a spinning ball of charge features a dipole moment, since every little charged particle within the ball travels during a circle when the whole ball is spinning. 

The moment of a magnet of a spinning ball of charge points along the axis of rotation.