The figure below shows a model eye 10 times the actual size of the human eye. The model is filled with water. A thin glass wall at the front acts like a cornea, forming a spherical surface for the water. The crystalline lens is represented by a thin glass lens immersed in the water.

(a) Find the focal length of the lens necessary to form an image of a distant object on the retina.(b) Find the focal length of the lens necessary to form a retinal image of an object 47.8 cm in front of the cornea.

http://d2vlcm61l7u1fs.cloudfront.net/media%2F056%2F05699c68-cd37-4bda-8f7d-67bc4b669cd4%2Fphpadizaf.png