The version of the lensmaker's equation we've thus far been using in class assumes that the lens is surrounded by air which has index of refraction Nair 1. More generally, if a lens is surrounded by an "outer" medium of index nout, then the lensmaker's equation becomes.
If Judah is swimming under water and opens his eyes, we can model the optical power of his lens with this more general lensmaker's equation by choosing nout = "water = 1. 33. Will the minimum optical power of his eye increase, stay the same, or decrease when he's underwater as compared to in air? How much will it change? If Judah's vision is emmetropic in air, will it be myopic, emmetropic, or hyperopic under water? Draw ray diagrams depicting his vision of a distance object in air versus under water to visually make sense of all this. Can Judah's unaided eye focus on anything under water?