IV. Specific inductive capacity of dielectrics when acted on by very rapidly alternating electric forces

Abstract

The researches of Dr. John Hopkinson have shown that in some dielectrics, of which the most conspicuous example is glass, the refractive index is not, as it ought to be on Maxwell’s theory, equal to the square root of the specific inductive capacity, when the latter is measured for steady forces, or such as are reversed only a few thousand times a second. It is therefore desirable to measure the inductive capacity under circumstances which approach as nearly as possible to those which, according to Maxwell’s theory, occur when light passes through a dielectric. This will be when the forces are reversed as rapidly as possible. In the following experiments the forces were reversed about 25,000,000 times per second.