Question: Olive Oyal, a promising young physicist, has decided to recreate Millikan's famous oil-drop experiment using modern materials. Rather than employing oil, Olive chooses precision glass microspheres of diameter 1.0 μm and density 2.5gcm-3. Figure 9.10 illustrates her experimental apparatus and three spheres A, B, and C. Olive observes that
(1) before the switch is closed, all three spheres fall with the same speed , and
(2) after the switch is closed, sphere A rises with speed vf , sphere B falls with speed , and sphere C comes to rest.
Fig. - Charged glass microsphere between two plates which a voltage can be applied. Arrows show direction of motion when the switch is closed.
a. Based on the information given above, specify whether the charge on each of the three drops is +, -, 0, or indeterminate.
b. Prove that the mass of each sphere is equal to 1.31pg.
c. Now calculate the charge on each of the three spheres. From these results what might Olive conclude is the basic, elementary, unit of charge?