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

Answer

D

Explanation

For a normal eye, when relaxed, the eye lens offers minimum power, which is given as
`P = 40 D + 20 D = 60 D`
As rays from infinity are focussed on the retina, therefore, distance between retina and cornea eye
lens `= f = (1)/(P) = (1)/(60) m = (100)/(60) cm = 1.67 cm`.