GKFix MCQ Question

In the lens maker's formula 1/f = (n2/n1 - 1)(1/R1 - 1/R2), what do R1 and R2 represent respectively?

• A. R1 is the object distance, R2 is the image distance
• B. R1 is the inner radius, R2 is the outer radius
• C. R1 is the radius of curvature of the first surface, R2 is the radius of curvature of the second surface
• D. R1 is the focal length, R2 is the radius of curvature