Electromagnetic Lateral Waves Observed by Earth–Sounding Radars

Electromagnetic waves refracted at the critical angle according to Snell's law give rise to the lateral wave. The low amplitude lateral wave is usually obscured by other waves when continuous wave sources are used. Using a pulsed source (radar) and continuously recording echoes reflected from within dielectric earth materials as a function of angle of incidence, records are produced which clearly show the lateral wave. In some earth–probing applications, the lateral wave may predominate and proper identification of its characteristics is important.