1. The problem statement, all variables and given/known data An object is placed 60 cm from a thick double convex lens, with faces of radii of curvature 20 cm and 30 cm, with thickness of 2 cm, and index of refraction is 1.5. Find the position of the image. Ans: ( 39.9 cm) 2. Relevant equations lens maker's equation, na/object + na/image = (nb - na)(1/R1 - 1/R2) 3. The attempt at a solution I used this equation and got 40 cm, as opposed to 39.9. I figured it couldn't be a rounding error considering the numbers given. Am I supposed to use the 2 cm thickness somehow?