A plano-convex lens has index of refraction n. The curved side of the lens has radius of curvature R and rests on a flat glass surface of the same index of refraction, with a film of index nfilm between them, as shown in Fig. 37.18a. The lens is illuminated from above by light of wavelength &. Show that the dark Newton’s rings have radii given approximately by where m is an integer and r is much less than R.