Q. A slide projector needs to create a 97 cm high image of a 2.0 cm tall slide. The screen is 250 cm from the slide. Assume that it is a thin lens. What focal length does the lens need?
Q. Two small identical conducting spheres are placed with their centers 0.10 m apart. One is given a charge of 8 10-9 C, the other a charge of -12 10-9 C.
(a) Find the electrostatic force exerted on one sphere by the other.
(b) The spheres are connected by a conducting wire. Find the electrostatic force between the two after equilibrium is reached.