Refraction of Light Waves by Electrons

Abstract

IT is an established fact that wireless signals transmitted from any place are readily received at the diametrically opposite place on the globe. The explanation usually given of the phenomenon is that the ions in the Heaviside layer make the speed of propagation of the waves greater in that layer than in the ordinary air below and thus bend the waves round the earth by a process of refraction. Larmor has developed the mathematical theory of the refraction (Phil. Mag., December 1924), and has shown that if c is the velocity of light in vacuum and c′ in the presence of electrons, then c and c′ are related by the equationwhere N is the number of electrons per unit volume, e and m are the charge (in e.m.u.) and the mass of an electron, and λ the wave-length. Assuming λ = 10⁵ cm. for radio waves, calculations show that an electron density of 0.3 per c.c. is enough to produce the observed bending round the earth.