Scattering from finite square barrier

[bobred]

Homework Statement

Use the boundary conditions to show that

\frac{A+B}{A-B}=\frac{k_1}{k_2}\frac{C+D}{C-D}=\frac{k^2_1}{k^2_2}

Homework Equations

A+B=C+D and k_{1}A- k_{1}B = k_{2}C- k_{2}D

C e^{i k_{2}L}+D e^{- ik_{2}L} = F e^{i k_{1}L} and k_{2}C e^{ ik_{2}L}- k_{2}D e^{-i k_{2}L} = k_{1}F e^{i k_{1}L}

k_2 L=\pi/2

The Attempt at a Solution

I find

\frac{A+B}{A-B}=\frac{k_1}{k_2}\frac{C+D}{C-D}

but cannot seem to find

\frac{k^2_1}{k^2_2}

Its probably really simple.
Bob

 

[mfb]

k_1(A-B)=k_2(C-D)
Use this to replace (C-D) in the last equation, and replace (C+D) by (A+B) in the numerator.