\[\begin{align} ϕ_I (x) &= A 0 e^{ i k_0 x} + B_0 e^{ − i k_0 x} , \label{6.7} \\[5pt] ϕ_{II} (x) &= A_1 e^{ i k_1 x} . \label{6.8} \end{align} \] We define a transmission (\(T\)) and reflection (\(R\)...\[\begin{align} ϕ_I (x) &= A 0 e^{ i k_0 x} + B_0 e^{ − i k_0 x} , \label{6.7} \\[5pt] ϕ_{II} (x) &= A_1 e^{ i k_1 x} . \label{6.8} \end{align} \] We define a transmission (\(T\)) and reflection (\(R\)) coefficient as the ratio of currents between reflected or transmitted wave and the incoming wave, where we have canceled a common factor \[\begin{align} A_1 &= \dfrac{2 k_0}{ k_0 + k_1 A_0} \label{6.12} \\[5pt] B_0 &= \dfrac{k_0 − k_1 }{k_0 + k_1 A_0} , \label{6.13} \end{align} \]
