Horizontal linearly polarised light (at to the horizontal) passes through an ideal…
PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Polarisation and anisotropic media · Polarisation and anisotropic media
Optics and Photonics, Ch Birefringence and crystal optics
Problem
Horizontal linearly polarised light (at 0∘ to the horizontal) passes through an ideal half-wave plate (Γ=π) whose fast axis is set at 20∘ to the horizontal. A student's solution reads: "A half-wave plate rotates the polarisation of the light through the angle of its fast axis. Since the fast axis is at 20∘, the light leaves the plate linearly polarised at 20∘ to the horizontal."
((a)) Explain what is wrong with this reasoning.
((b)) Find the correct angle, to the horizontal, of the light leaving the plate.