Measuring the Faraday effect in olive oil using permanent magnets and Malus' law.

We present a simple permanent magnet set-up that can be used to measure the Faraday effect in gases, liquids and solids. By fitting the transmission curve as a function of polarizer angle (Malus' law) we average over short-term fluctuations in the laser power and can extract phase shifts as small as ± 50 μrads. We have focused on measuring the Faraday effect in olive oil and find a Verdet coefficient of V = 192 ± 1 deg T-1 m-1 at approximately 20 °C for a wavelength of 659.2 nm. We show that the Verdet coefficient can be fit with a Drude-like dispersion law A / (λ2 - λ0 2) with coefficients A = 7.9 ± 0.2 × 107 deg T-1 m-1 nm2 and λ0 = 142 ± 13 nm