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The Faraday effect or Faraday rotation, sometimes referred to as the magneto-optic Faraday effect (MOFE), [1] is a physical magneto-optical phenomenon. The Faraday effect causes a polarization rotation which is proportional to the projection of the magnetic field along the direction of the light propagation.
Faraday rotation is a rare example of non-reciprocal optical propagation. Although reciprocity is a basic tenet of electromagnetics, the apparent non-reciprocity in this case is a result of not considering the static magnetic field but only the resulting device.
Kerr rotation and Kerr ellipticity are changes in the polarization of incident light which comes in contact with a gyromagnetic material. Kerr rotation is a rotation in the plane of polarization of transmitted light, and Kerr ellipticity is the ratio of the major to minor axis of the ellipse traced out by elliptically polarized light on the plane through which it propagates.
Optical isolators are different from 1/4 wave plate based isolators [dubious – discuss] [clarification needed] because the Faraday rotator provides non-reciprocal rotation while maintaining linear polarization. That is, the polarization rotation due to the Faraday rotator is always in the same relative direction.
In contrast, the Faraday effect is non-reciprocal, i.e. opposite directions of wave propagation through a Faraday medium will result in clockwise and anti-clockwise polarization rotation from the point of view of an observer. Faraday rotation depends on the propagation direction relative to that of the applied magnetic field.
In a magnetic field, even substances that lack chirality rotate the plane of polarized light, as shown by Michael Faraday. Magnetic optical rotation is known as the Faraday effect, and its wavelength dependence is known as magnetic optical rotatory dispersion. In regions of absorption, magnetic circular dichroism is observable.
Electromagnetic rotation experiment of Faraday, 1821, the first demonstration of the conversion of electrical energy into motion [48] In 1821, soon after the Danish physicist and chemist Hans Christian Ørsted discovered the phenomenon of electromagnetism, Davy and William Hyde Wollaston tried, but failed, to design an electric motor. [3]
Electromagnetic rotation experiment of Faraday, ca. 1821 [2] Working principle of a homopolar motor: due to movement of negative charges from center towards rim of the disk, a Lorentz force F L is created which brings the entire disk into rotation. The homopolar motor was the first electrical motor to be built.