1. The problem statement, all variables and given/known data The cornea, a boundary between the air and the aqueous humor, has a 3.0cm focal length when acting alone. What is its radius of curvature? 2. Relevant equations n(1)/s + n(2)/s' = (n(2)-n(1))/R where, n is the index of refraction (unitless), s' is the img dist (cm). and s is the obj. dist (cm). R is the radius (cm). also, 1/s + 1/s' = 1/f where, f is the focal length. also, n(1) is air having a index of refraction of 1.00 and n(2) is the aqueous humor having a index of refraction of 1.34 3. The attempt at a solution So, I assumed since only f was given as 3.0cm that 1/s' + 1/s could be 1/6.0cm + 1/6.0cm = 1/3.0cm. Then that would give 1.00/6.0cm + 1.34/6.0cm = (1.34-1.00)/R giving R to be 0.87cm but it says that is wrong. Any ideas??? Also, I thought there was a equation editor for this website? I can't seem to see it... Is it only for the premium members?