The drawing shows a cross section of a plano-concave lens resting on a flat glass plate. (A plano-concave lens has one surface that is a plane and the other that is concave spherical.) The thickness t is 1.35 * 10^-5 m. The lens is illuminated with monochromatic light (lambda vacuum = 570 nm), and a series of concentric bright and dark rings is formed, much like Newton's rings. How many bright rings are there?