Let the current 'I' be associated with an electron of charge 'e' moving in a circular orbit of radius ' r ' with speed ' v ' around the positively charged nucleus. The ratio r v is

Step-by-step solution

The current I for an electron of charge e in a circular orbit equals the charge passing a point per unit time. Since charge e passes a point each revolution period T , the current is given by I = e T . The time period for one orbit is T = 2 r v , where r is the radius and v is the orbital speed. Combining these yields I = e 2 r v = ev 2 r . Rearranging to solve for the ratio r v gives r v = e 2 I . This expression corresponds to option C.