The diameter of the eye ball of a normal eye is about 2.5cm. The power of the eye lens varies from

Options

A. 9D to 8D
B. 40D to 32D
C. 44D to 40D
D. None of these

Answer

C

Explanation

An eye see distant objects with full releaxtion.
So, `(1)/(2.5xx10^(-2))-(1)/(-oo)=(1)/(f)`
or `P=(1)/(f)=(1)/(2.5xx10^(-2)=40D`
An eye see an object at 25cm with strain
`(1)/(2.5xx10^(-2))-(1)/(25xx10^(-2))=(1)/(f)`
`therefore P=(1)/(f)=40+4=44D`
The power of the eye lens various from 44D to 40D.