1. The problem statement, all variables and given/known data A double concave lens has equal radii of curvature of 15.1 cm. An object placed 14.2 cm from the lens forms a virtual image 5.0 cm from the lens. What is the index of refraction of the lens material? A. 1.98 B. 1.9 C. 1.84 D. 2.06 2. Relevant equations 1/f = (n – 1 ) (1/R1 - 1/R2 ) 1/f = 1/do + 1/di 3. The attempt at a solution 1/f = 1/14.2 + 1/5.0 so i get 1/f = 0.27 1/f = (n – 1 ) (1/R1 - 1/R2 ) 0.27 = (n-1) (1/15.1 - (-1/15.1) this results in an n equal to about 3.03 which is not close to any of the answers, though I'm sure i have the right equations, I'm just not sure what i'm doing wrong? are these only applicable to convex lens?