Schematic view of the base wave transmission-reflection problem. An incident wave energy ray in the cavity C_n with an amplitude of encounters a barrier located between the radii and , and associated with the (complex) reflection and transmission coefficients R_{n, n + 1} and T_{n, n + 1}. A part of the energy ray is reflected back into the cavity C_n with an amplitude of , and another part is transmitted into the overlying cavity C_n + 1 with an amplitude of .