4. The interface between two conducting materials can be modelled as a delta- function potential barrier, V(x) = 76(x) with y > 0, so that Schrodinger's equation becomes 2m dx2 + (x)0 = EQ A particle is incident from the left ( 0) With a = ym/h2k prove that 1 B ia and 1 + ia A 1 + ia and show that the probabilities of transmission and reflection add up to unity