l. Prove that R + T = l, for the case of a step potential with E > V0 , where B*B kl _k2 * k1_k2 k1 \"-kz 2 R A*A (k1 + k2) (k1 + k2 k1 + k2 > 0 T _ 59; (2km _ 4k1k2 k1 (k1 + k2)2 (k1 + k2)2