A unified picture of plane wave reflectivity from a liquid-solid interface and a solid plate in a liquid

The ultrasonic plane wave reflection coefficient for a solid plate immersed in a liquid must be reducible to that for a liquid-solid interface as the solid plate thickness becomes very large. This can be achieved when absorption is taken into account. The calculated results describe the reflectivity characteristics of a thick solid plate and provide practical criteria to determine the lower limit of the solid sample thickness that can be considered as a half-space. [This work was supported by the Office of Naval Research, U.S. Navy, and the Scientific Affairs Division, NATO.]