a.) Consider a concave lens with the following parameters: where a is the lens's width across an end, b is the width across the middle, L is the length of the lens, d is the depth of curvature, and R is the radius of curvature. In finding an expression for the radius of curvature R in terms of a, b, and L, provide a trigonometric or algebraic reason for each of the following steps: Why is this true Step d² + (L²/4) Result of Prelab 3, which applies here as R = 2d well. d=a-b R = R = [(a - b)2/4]+(L²/4) (a - b) (a - b)² + L² 4(a - b)