Consider a double convex lens that has two surfaces of equal radii R and a refractive index m = 1.5 . The focal length f is given by:

Step-by-step solution

Using the lens maker's formula: 1 f = (m - 1) ( 1 R₁ - 1 R₂ ) For a double convex lens, the radii of curvature are R₁ = R and R₂ = -R . Given m = 1.5 : 1 f = (1.5 - 1) ( 1 R - 1 -R ) 1 f = 0.5 ( 2 R ) 1 f = 1 R f = R