I have a question in which we are instructed to find the separation distance between the two impact zones of Sodium atoms on a photographic plate: A magnet of length l= 0.15m and field gradient [tex]\nabla[/tex]B= 9.0T/m over its full length is used in a Stern-Gerlach experiment. If a beam of Sodium atoms of velocity v=600m/s passes through this magnet and then strikes a photographic plate at a distance of d=0.80 m beyond the magnet, what will the separation between the two impact zones be on the film? Sodium has total-angular momentum of J=1/2, contributed by the spin of an electron of the 3s subshell. I understand that as the electrons enter the magnet, half of the electrons will experience spin-up or spin-down depending if s is positive or negative and thus, there are only two permitted magnetic moments which gives two impact zones on the photo film. However, I am confused as to how to find the distance between the two impact zones based on the information given. Any assistance is welcome! Thanks!