1. The problem statement, all variables and given/known data I am trying to calculate the transmission and reflection coefficients for rectangular finite potential barrier between (-a, a) for a particle of mass m with energy equal to the height of the barrier (E = V0 > 0). 2. Relevant equations http://en.wikipedia.org/wiki/Rectangular_potential_barrier#E_.3D_V0 3. The attempt at a solution I understand the general solutions for the potential region are linear, and am trying to match the boundary conditions to evaluate the coefficients, but I am having trouble understanding why the Wikipedia page linked above has the imaginary number disappear from the exponentials attached to the Cl term. Instead there is just a + sign there. Is this just a mistake on the page? As far as I can tell, there is no reason the term should suddenly become real.