An electron is confined to a rectangle with infinitely high walls.I need to calculate the ground state energy of the electron. Can I treat a rectangle with infinite high walls to be the same as 2d box as mentioned here. http://en.wikipedia.org/wiki/Particle_in_a_box or it should be treated in some other way. The problem mentions rectangle and not rectangular box as such, but since high walls are mentioned I thought it should be treated as 2d. Will this apply for rectangle with high walls?. For the 2-dimensional case the particle is confined to a rectangular surface of length Lx in the x-direction and Ly in the y-direction. I think infinite high walls is mentioned only to inform us that the potential is zero inside the rectangle and infinite at the walls. If the rectangle had side lengths in nanometers can we still treat it as a 2-dimension box problem. Regards. QP.