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

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

(a) 9 D to 8 D
(b) 40 D to 32 D
(c) 44 D to 40 D
(d) None of these

44 D to 40 D

An eye see distant objects with full relaxation.

So, [1 / (2.5 × 10⁻²)] – [1 / -∞] = 1 / f or, P = 1 / f = 1 / 2.5 × 10⁻² = 40 D

An eye see an object at 25 cm with strain [1 / (2.5 × 10⁻²)] – [1 / 2.5 × 10⁻²] = 1 / f

.·. P = 1 / f = 40 + 4 = 44 D

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