A convenient method for measuring the dc Kerr effect on the stage of a polarizing microscope is described. Two novel illustrations of this technique are presented: a low-field determination of the pretransitional Kerr effect in the isotropic phase of a nematic having a negative dielectric anisotropy and measurements of the birefringence on both sides of the nematic-isotropic ($N-I$) phase boundary as the $N-I$ critical point is approached by applying very high electric fields to a nematic with positive dielectric anisotropy.

• Received 2 July 1984

DOI:https://doi.org/10.1103/PhysRevA.30.3156