 Solution

ID: past-exam-of-the-physics-a-course-of-the-university-of-cambridge/2013/paper-2/section-b/b6/a/solution

Substituting

Z_{j} = T ρ_{j}

into the junction formula gives

\frac{P _{r}}{P _{i}} = (\frac{ρ _{1} - ρ _{2}}{ρ _{1} + ρ _{2}})^{2}, \frac{P _{t}}{P _{i}} = \frac{4 ρ _{1} ρ _{2}}{( ρ _{1} + ρ _{2} ) ^{2}} .

Equal densities give zero reflection; a very large mismatch gives nearly complete reflection. reflection from the higher-impedance side reverses displacement phase.

 New to topics? Read the docs here!