Question

Calculate the focal length of a corrective lens having power +2.5 D.

Answer 1

Solution: Data: Convex lens, P = +2.5 D, f = ?

P = 1/f

∴ 2.5 D = 1/f

∴ f = 1/2.5D = 0.4m = 40cm

The focal length of the lens is 40 cm.