Question

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

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

Answer 1

The correct option is C $1.67$ cm

(lens + cornea) should form image of distance object at retina
Converging power (40 + 20) D = 60 D
Using lens equation
$\frac{1}{v}-\frac{1}{\infty }=\frac{60}{100}$
$v=\frac{5}{3}cm=1.67cm$
So distance between retina and cornea should be$1.67$ cm.