Scottish physicist who found that compression in one direction causes an isotropic solid to exhibit double refraction (birefringence ). He showed that complete polarization occurred (only one polarization was reflected) when the reflected and refracted rays were perpendicular, a phenomenon which occurs at what is now known as Brewster's angle. He also studied biaxial crystals, and showed that some exists in which two axes do not exhibit double refraction, whereas in a uniaxial crystal like calcite, there is only one such axis. Finally, he showed that plane polarized light falling on a metal is plane polarized after reflection if it is parallel or perpendicular the plane of reflection, otherwise it is elliptically polarized.

Additional biographies: Bonn