I started learning Quantum mechanics(one dimension) a week ago and I came across solving the Schrodinger equation for a particle in a box with zero potential.I found out that there are only certain energy levels permissible for that particle. My query is if we take a large number of boxes with a particle in each, how will be the relation of number of boxes that have a given energy? Is that something governed by a law? Or does it depend on any physical condition? If so, what may it be?