Consider a particle moving in a one-dimensional potential-energy well (box) with infinitely high walls. The potential energy of the particle inside the well is U = 0 and outside the well U = infinity. The wave function describing this system is Psi_n(x) = (2/L)^(1/2) * SIN(nπx/L) for 0 ≤ x ≤ L. Psi_n(x) = 0 otherwise, where n = 1, 2, 3, ....