Schematic view of a star modeled as an ensemble of resonant cavities, {C_i}_{1 ≤ i ≤ N}, where the waves can propagate and the JWKB approximation is met. The cavities are separated from each other by barriers corresponding to either evanescent or rapidly varying regions associated with complex reflection and transmission coefficients R_{i, i + 1} and T_{i, i + 1} (gray shaded regions). The lower and upper boundaries of the cavity C_i are located at the radii and . The upward and downward energy ray in the cavity C_i are associated with the amplitudes and , respectively, where the plus (minus) sign is chosen when the origin of the wave phase in Eqs. (11) and (12) is chosen at (). The boundaries at the stellar center and surface are modeled as totally reflective barriers.