A person wear normal spectacles in which the distance between glasses and eyes is approximately 2 ~cm , then power required is -5 D. If he wears contact lens, then the required power is

Step-by-step solution

Contact lens is more effective, so its required power is less. For glasses: aligned & 1 v - 1 u = 1 f 1 -x - 1 = 1 f & f=-x ~cm =- x 100 ~m & Power, P= 1 f =- 100 x =-5 x=20 ~cm aligned If he used contact lens then aligned & u=- , v=-22 ~cm & 1 v - 1 u = 1 f 1 -22 = 1 f & f=-22 ~cm , P=- 100 22 D =-4.54 D aligned