1. The problem statement, all variables and given/known data A lens of power of -5.0D has a surface which is convex of radius of curvature of 15.0cm. The lens is made of material of refractive index of 1.50. What's the radius of the other surface of lens? 2. Relevant equations 3. The attempt at a solution since power = 1/f so i have (1/ (-1/5) )= ( (1.5-1)/ 1) x ( (1/15) + (1/r2) ) i found out my r2 = -0.10cm. But the correct ans given is -6.0cm.