For a normal eye, the cornea of eye provides a converging power of `40 D` and the least converging power of the eye lens behind the cornea is `20 D`. Using this information, the distance between the retina and the cornea eye lens can be estimated to be

Options

A. 5 cm
B. 2.5 cm
C. 1.67 cm
D. 1.5 cm

Answer

C

Explanation

(lens + cornea) should form image of distance object at retina Converging power `(40 + 20) D = 60 D`
Using lens equation
`(1)/(v)-(1)/(oo)=(60)/(100)`
`v=(5)/(3)cm=1.67 cm`
So distance between retina and cornea should be 1.67 cm.