On the basis of the 2D analytic theory of the phenomenon of frustrated total internal reflection for a Gaussian light beam, produced by the authors in the previous paper [J. Opt. Soc. Am. A32, 843 (2015)JOAOD60740-323210.1364/JOSAA.32.000843], the efficiency of waveguide mode excitation in a plane dielectric layer using a prism is considered. The influence of the initial beam half-width, of the thickness of a waveguide, and of its displacement from the prism base on excitation efficiency is investigated. The conditions of maximal efficiency are established.