Question

If diameter of human eye is 2.5cm, find the power range of the eye

Answer 1

For clear vision, the image must be on the retina. Let $d=2.5\,cm=0.025\,m$, $d_0=\infty,\, d_1=0.25\,m$ for diameter of human eye, distant vision and close vision respectively. We have $P_i=\frac{1}{d_i}+\frac{1}{d}$ for power of a lens.

Hence the power of the eye ranges from $P_0=40\, D$ (for distant totally relaxed vision) to $P_1=44\,D$ (for close fully accommodated vision).