Disappearance and reversal of the Kerr effect

Abstract

A beautiful confirmation of recent theories of the electric birefringence in liquids (C. V. Raman and K. S. Krishnan, Phil. Mag., April 1927) is furnished by observations of the phenomenon in electric fields oscillating with radio-frequency such as may readily be obtained with thermionic valves. The Kerr effect arises from the orienting action of the field on the molecules, and the time taken by the latter to adjust themselves to a state of statistical equilibrium has naturally to be taken into account. It may be pointed out here that the orienting couple acting on the permanent electric moment of the molecule (assumed to be chemically polar) stands on a different footing from the couple acting on the oscillating induced moment in it. The couple acting on the permanent moment is purely periodic, and its effect must tend to disappear at sufficiently high frequencies. The couple on the induced moment, on the other hand, has a quasi-static part and tends to persist even at optical frequencies.