An ion separator consists of a uniform magnetic field that is directed into the plane of the page and two conducting plates that can be charged with equal magnitudes of charge but of opposite sign. A student wants to launch negatively charged ions into the ion separator at velocity such that the ions pass through the ion separator undeflected. However, the student also wants to launch positively charged ions at velocity v such that the ions cannot pass through the separator. The magnitudes of charge for a positive ion and for a negative ion are the same in this experiment. Based on the figure, which one of the two plates, if any, should be positively charged, and why? (A) B X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X D The bottom plate, because the magnetic force exerted on the negative ion will be toward the top plate. Therefore, the electric field must point toward the top plate. The top plate, because the magnetic force exerted on the negative ion will be toward the top plate. Therefore, the electric field must point toward the bottom plate. The top plate, because the magnetic force exerted on the negative ion will be toward the bottom plate. Therefore, the electric field must point toward the bottom plate. Neither plate, because the situation cannot be created with the plates as shown. An electric field must be oriented parallel to the plane of the page. Neither plate, because this situation cannot be created. If the electric force and magnetic force for the negatively charged ions cancel such that the ion travels through the region undeflected, the same would also be true for the positively charged ions.