Use of phase-sensitive amplifiers for high precision measurements: Faraday constant determination with an alternating or static magnetic field

In this work, we present some of the fundamental concepts which explain how lock-in amplifiers work and how they can be explored to design experimental methods for precise physical quantity measurements. More specifically, we propose to use a dual-phase lock-in amplifier in two simple experiments for measuring Verdet constant at weak alternating and static magnetic field conditions. We characterize water and ethanol and mixtures of the two solvents since these liquids are abundant, low cost, easy to handle, and have small Verdet constants, being suitable for testing the sensibility and precision of the experiments. Also, we studied the chromatic dispersions by measuring the Verdet constants in three different wavelengths: 480 nm, 540 nm and, 640 nm. Good results could be confirmed by the fair agreement between the data obtained with the two type of magnetic fields and, also, with values found in the literature.

Keywords
Lock-in; Faraday rotation; Malus Law; Refractive index dispersion