Calculate the power of the eye lens of the normal eye when it is focused at its

(a)Far point (infinity) and

(b)near point (25cm from the eye).

Assume the distance of the retina from the eye lens to be 2.5cm.

a) The object at infinity is imaged at the retina. As the eye lens is a convex one, so the focal length will be 2.5 cm.
Power of the lens=100f=1002.5=40 D
b) in this case,
u=25 cmv=2.5 cmf=?
For the convex lens,
1v+1u=1f12.5+125=1f1f=1125
Power of the lens,
P=100f=100×1125=44 D

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