The near point of a person suffering from hypermetropia is 75cm. Calculate the power of lens required to enable him to read the newspaper which is kept at 25cm from the eye.

Here, image distance, v = -75 cm 

object distance, u = -25 cm 

so, the focal length will be 

1/f = 1/v - 1/u 

or 

1/f = 1/25 - 1/75

 or 

1/f = 0.027

thus, f = 37.03 cm = 0.37 m

 the power of the lens would be, 

P = 1/f so, P = 1/0.37 = 2.70 Dioptre