Question

Explain the least distance of distinct vision.​

Answer 1

$\large\boxed{\fcolorbox{blue}{yellow}{Answer:-}}$

The human eye can normally focus objects from about 25 cm to infinity by changing the focal length of the crystalline lens. The short focal length of the lens required for near vision is produced by contraction of the ciliary muscles. Thus, to fix focus on an object held very close to the eye produces considerable strain on the ciliary muscles. The minimum distance at which the eye can focus without any strain is called the near point or the $\bf\large\underline\red{least \:distance \:of \:distinct</p><p>\:vision.}$ The least distance of distinct vision is taken to be 25 cm, approximating to that of the normal eye of a young adult.

[$\bf\large\underline\red{Note:-}$: The near point recedes with age, from about 7 cm for a child 10 years old to about 200 cm for an adult 60 years old.]