My head's melting right now, because I've been stuck on this for the past 6 hours. There's a particle of mass moving in a potential well where V(x) = infinity at x<0 V(X)=0, 0<x<a V(x)= Vo, x>a Vo>0 E<Vo I'm assuming that the wavefunction at x<0 is 0, since there's an infinite potential there. The energy inside the potential well is just the kinetic energy, =(Hk)^2/2m, where H=h/2pi, so the wavefunction should be of the form psi= Aexp(-ikx ) Now outside the well, at x>a, the energy should be E= Vo-Ek because the particle is bound in the well. We then get psi=Bexp(-Tx), where T is k with (Vo-E) instead of E. Am I wrong in assuming this? When I try to find the radius using X^2 + y^2 = R^2, where x=k=a*sqrt(2mE)/H and y=ai*(sqrt(2m(Vo-E))/H I get out a negative radius. Please help me see what I've done wrong, I'm sure I've got the energy value on the finite potential side wrong, but I can't see how.