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# Faraday Rotation measurement of the Verdet Constant of SF-57 glass at 650 nm: Third Draft

Abstract

Light emitted from a laser was directed into a solenoid, with a glass rod inside, and then into a polarizer to measure the angle of rotation. As we changed the polarizer angle, the intensity of the light followed a cosine squared function. A Verdet constant is specific to each medium which describes the wavelength dependent optical strength. Three different methods were used to determine the Verdet constant of the glass rod (SF-57): 1) directly measuring the shift angle with and without an applied magnetic field, 2) measuring the voltage proportional to light intensity at a particular angle while changing the field, 3) using an alternating current to generate an alternating field to measure the corresponding alternating voltage. We measured a Verdet constant of 0.0189 $$\pm$$ 0.0017 $$\frac{radians}{mT\cdot m}$$, 0.01856 $$\pm$$ 0.00016 $$\frac{radians}{mT\cdot m}$$, and 0.0177 $$\pm$$ 0.0006 $$\frac{radians}{mT\cdot m}$$ for methods one, two and three respectively. The values are in agreement with each other, and they also agree with the literature.

## Aims

The Faraday Rotation of Polarized light is the rotation of the plane of polarization of light propagating through a medium due to the presence of a magnetic field. In this experiment, we aim to measure the Verdet constant of a glass rod (SF-57) through the Faraday Effect.

## Introduction

By 1845, it was understood that different materials change the polarization of light. Michael Faraday was searching for evidence that the electric force affects the polarization of light. At the time, the experimental methods were not sensitive enough to measure this change of polarization; however, when light passes through various substances Faraday was able to observe this change. Therefore, this is called the Faraday effect. To quote Faraday in his daily journals, “but when the contrary magnetic poles were on the same side, there was an effect produced on the polarized ray, and thus magnetic force and light were proved to have relation to each other.”

The Faraday Effect measures the polarization of light going through an active medium inside a magnetic field. The Faraday effect causes light to rotate as it goes through a magnetic field. And this rotation of polarization is linearly proportional to the component of the magnetic field.The degree of rotation depends on the color of light, the length of the magnetic field (L), and the properties of the medium the light goes through.