Transonic potential flow over an infinitely-long two dimensional wall, corrugated in the shape of harmonic waves, has been calculated using Murman's finite difference scheme based on transonic small perturbation theory. The calculated flow characteristics are presented using transonic similarity parameter. The growth and decay with the free stream Mach number of the local supersonic regions in subsonic main stream and the local subsonic regions in supersonic main stream has been quantitatively investigated in transonic flow regime. In this connection, two critical similarity parameters, low and high, are defined and evaluated. Comparison with other literature was possible only for the part of subcritical flow and excellent agreement was obtained for the present calculation with the analytic solution available.