A double-concave lens has equal radii of curvature of 15.1 cm. An object placed 14.2 cm from the lens forms a virtual image 4.94 cm from the lens. What is the index of refraction of the lens material?
A fisherman in a stream 57 cm deep looks downward into the water and sees a rock on the stream bed. How deep does the stream appear to the fisherman? Assume that the index of refraction of the water is 1.33.