Question

Why probability current density is zero in clasdically forbidden region?

Answer 1

First, the wave function can be non-zero in a classically forbidden regime, and its square magnitude does give the probability of that happening—rather, since it's a probability density, you have to integrate over a range to find the probability of being somewhere in that range.In quantum mechanics, the probability current(sometimes called probability flux) is a mathematical quantity describing the flow of probability in terms ofprobability per unit time per unit area. ... It is a real vector, like electric current density.