The three regions shown in Fig. 8-32 (P8.9) contain perfect

The three regions shown in Fig. 8-32 (P8.9) contain perfect dielectrics. For a wave in medium 1 incident normally upon the boundary at z = – d, what combination of ?r2 and d produce no reflection? Express your answers in terms of ?r1, ?r3 and the oscillation frequency of the wave, f.