College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 15

The lens-maker's equation applies to a lens immersed in a liquid if n in the equation is replaced by n 1 / n 2. Here n 1 refers to the refractive index of the lens material and n 2 is that of the medium surrounding the lens. (a) A certain lens has focal length of 79.0 cm in air and a refractive index of 1.55. Find its focal length in water. (b) A certain mirror has focal length of 79.0 cm in air. Find its focal length in water.