1. The problem statement, all variables and given/known data A particle of charge q and a mass m, moving with a constant speed v, perpendicular to a constant magnetic field B, follows a circular path. If in this case the angular momentum about the center of this circle is quantized so that [tex]mvr_n = 2nh[/tex], determine the allowed radii for the particle in terms of n, h, q, and B for n = 1,2,3,.... 2. Relevant equations [tex]F = qvBsin\vartheta [/tex] 3. The attempt at a solution As far as I can tell, this has something to do with relating magnetism to the quantum level. It is easy enough to calculate the radius at a given energy level by solving for [tex]r_n[/tex]. But I do not understand how to relate the charge and the B field to the situation. The best I can come up with is the formula provided... I feel like there is some way it ties into the problem. Help greatly appreciated.