Solution (source code)

= Solution

Substituting $Z_j=\sqrt{T\rho_j}$ into the junction formula gives
$$
\boxed{\frac{P_r}{P_i}=\left(\frac{\sqrt{\rho_1}-\sqrt{\rho_2}}{\sqrt{\rho_1}+\sqrt{\rho_2}}\right)^2,\qquad
\frac{P_t}{P_i}=\frac{4\sqrt{\rho_1\rho_2}}{(\sqrt{\rho_1}+\sqrt{\rho_2})^2}}.
$$
Equal densities give zero <reflection>; a very large mismatch gives nearly complete <reflection>. <reflection> from the higher-impedance side reverses displacement phase.