A simple calibration experiment for light dependent resistors using Malus law

Abstract

We demonstrate the use of polarization to characterize the nonlinear response of a light dependent resistor (LDR). Previous experiments use the inverse square-dependence of the irradiance to calibrate the LDR’s response. In our study, we employ cross-polarizers to vary the irradiance incident on the surface of the LDR. We integrate the LDR into a simple voltage divider circuit and measure the voltage response as we rotate one of the cross-polarizers. We derive expressions that relate the voltage measurements to the angle between the polarizers. Our analytical predictions greatly match with the results obtained from the experiments; we then apply least squares method to get the calibration constants associated with the LDR’s nonlinear response. Finally, we discuss the advantages of our technique and emphasize its pedagogical benefits for high school and undergraduate laboratory courses.