Page:On the Determination of the Index of Refraction of Glass for the the Electric Ray.djvu/8

300 In the next series of observations, the rays were refracted from air into glass. The electric beam was rendered parallel with the help of a glass lens (f = 4 cm.). The beam was incident on the plane face of the semi-cylinder. As the cylinder itself focussed the refracted beam, the objective hitherto used in conjunction with the receiver was dispensed with.

Mean value of μ = 2·03 ........ (4).

The different values of μ obtained are given below:—

The frequency of vibration was of the order 1010.

The value of the optical index of the glass determined by the total reflection method was found to be