1. The problem statement, all variables and given/known data 10^12 positrons of the same kinetic energy are incident on 10eV, 1nm barrier. What is the minimum kinetic energy the positrons need before any of them can penetrate the barrier? 2. Relevant equations p_T = e^(-2*a*L) a = (sqrt(2m(V_0-E))/hbar 3. The attempt at a solution For other problems I've plugged numbers into these equations to find non zero probabilities but this time I'm not sure how to solve it. I tried setting p_T to zero and rearranging for E but that just ended up as V_0=E.