For this question, assume that the index of refraction of diamond is 2.39, that of glass is 1.65, that of water is 1.30, and that of air is extremely close to 1. A thin lens made of glass has a focal length in air of 16.1 cm. A lens of exactly the same shape is then made from diamond. HINT: Review the derivation of the thin lens formula. Note that the index of refraction, n, used in the derivation is actually the relative index of refraction: n = n lens/n surrounding a) What is the focal length of the diamond lens in air? b) What is the focal length of the diamond lens in when it is immersed in water? I was not sure at all how to even get started on this problem.