1. The problem statement, all variables and given/known data A thin converging lens has radii of curvature of R1=9cm and R2=-11cm. Assume its focal points F1 and F2 are 5cm from the center of the lens. Determine its index of refraction. 2. Relevant equations Len's Makers equation: 1/f = (n2 - n1 / n1) (1/R1 - 1/R2) 3. The attempt at a solution focal length f = 5cm n1 = air = 1 Plugging in all my known values: 1/5 = (n2 - 1) (1/9 - 1/11) n2 = 10.9 This value for refractive index doesn't make sense at all... so I'm not sure what I'm doing wrong!