Question

Problem 6. A fish's eye has a focal length of 1 cm in water (which is just the distance from the lens to the fish's retina, of course). Is its focal length in air longer or shorter? Don't just answer with a guess – you need to make a complete argument based on the lens-maker's formula or Snell's law directly, supported by pictures. Is the fish nearsighted or farsighted in air? Conversely, if you open your eyes underwater (and have normal vision in air) are you nearsighted or farsighted?

Answer 1

Jug Let refractive Index of eye lens is ne. leefractive index of air and water are na& no respectively then I when fish is inside water then rays are entering from water into eye then F = (wohe - -) -0 where R, and Ry be the radio of curvature of eye lens. Similarly when fish is in the air then light rays are entering from air into eye them! I = Cane-1) (1 - 1) @ dividing eq.0 by eq. - I k whe-1) (for lifa) = Came-1) S t 7 fa = hone-1) to Cone-1) o whle - Melno) = na < ( 7) ane (Melna) no => who cane - ② So from egun ③ and 4 - fa fafw So Jocal length of eye lens is smaller as Compared to water so days are focessed

earlier in case of air. So fish is mearsighted in the air Reverse will hapben if we open our eye. in water then we become farsighted.