Question

A beam of unpolarised light is incident on a detector measuring its intensity. Two linear polarisers and two half-wave plates are provided. The orientations of the fast and slow axes on the wave-plates are not marked. Suggest and explain a method for alignment of the axes of the two wave-plates. Is it possible to distinguish the following two configurations when (a) the fast axes of the wave-plates are aligned and (b) the fast and slow axes of the wave-plates are aligned? Justify your answer using appropriate mathematical derivations describing the modification of light polarisation when it propagates through the system of two linear polarisers and two wave-plates. [7 marks]