Q. Batman and Robin are attempting to escape that dastardly villain, the Joker, by hiding in a large pool of water (n=1.33). The Joker stands gloating at the edge of the pool. (His makeup is water soluble hence he won't jump in). He holds a powerful laser weapon 1.05 m above the surface of the water and fires at an angle of 27.7o to the horizontal. He hits the Boy Wonder squarely on the letter "R", which is located 3.8 m below the surface of the water. How far (horizontal distance) is Robin from the edge of the pool? (Fear not, Batfans. The "R" is made of a laser-reflective material).

2. Batman attempts to hide out in a Batbox. The top is a mirrored surface, but the vertical sides are made of a clear Batplastic (n=1.33). The box is located 3.42 m horizontally from the edge of the pool. What is the minimum depth (measured to the top of the Batbox) that the Batbox can be below the surface of the water for the Caped Crusader to remain hidden from the Joker? Suppose that the Joker gets down close to the water for the best view.

(a) Find out the electric potential, taking zero at infinity, at upper right corner (the corner without a charge) of the rectangle. (y = 3.8cm and x = 5cm)

(b) Repeat if the 2µC charge is replaced with a charge of -2µC.