WRRCTR No.25 Reflectivity of Electromagnetic Waves at an Air-Water Interface for Pure and Sea Water

Abstract

Compilation of the optical properties of electromagnetic waves incident on pure (chemically pure) or sea water shows an abrupt divergence of behavior for the two water types at about the 3-centimeter wavelength. From this point on to all longer (radio) wavelengths, sea water behaves optically like a metal, whereas pure water behaves like a semiconductor. At shorter wavelengths (below 3 centimeters), both fresh and pure water behave as dielectrics with similar optical properties. Only at visible wavelengths are the optics of natural waters of all salinities well known. The reflectivity contrast (difference in reflectivity divided by average reflectivity) between pure and sea water to visible light is approximately 3%. The reflectivity contrast between sea and pure water at radio frequencies is approximately 44%.