Question

A farsighted man uses eyeglasses with a refractive power of 3.13 diopters. Wearing the glasses 0.023 m from his eyes, he is able to read books held no closer than 0.260 m from his eyes. He would like a prescription for contact lenses to serve the same purpose. What is the correct contact lens prescription, in diopters?

Answer 1

Refractive power of eyeglasses,

Distance of the eyeglass from the eyese, d= 0.023m

Images is to be formed at a distance, v= -0.260m

Main difference between eyeglasses and contact lenses is that the eyeglasses are worn at a distance from eyes while contact lenses are worn on the eyes only.

Then object distance (u) for the eyes will be

Using given values in above,

  

Then power of contact lenses will be

using given and calculated values in above,

(ANS)