Question

for a normal eye the cornea of eye provides a converging power of 40D and the least converging power of eye lens behind the cornea is 20D. using the information , the distance between the retina and the cornea-eye lens can be estimated to be -

Answer 1

For a normal eye rays coming from infinity should go The rectina without any effort when we look at infinity,lens offers minimum power hence combination givesP=p1+p2
p=40D+20D=60D

Then the distance between rectina and cornea eye must be equal to focal length
f=1/p
f=1/60=1.67 cm