Question

Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

Answer 1

The eye lens is composed of a fibrous, jelly-like material. To see closure and distant object, Its focal length can me changed to certain extent by contraction and relaxation of ciliary muscles. The ability of the eye lens to adjust its focal length by contracting and relaxing its ciliary muscles is called accommodation. To see closer object, ciliary muscles, must decrease the focal length of eye lens. However, the focal length of the eye lens cannot be decreased below a certain minimum limit. To see an object comfortably and distinctly, the distance of object should be at least 25 cm from the eyes. Due to this, a normal eye is not able to see clearly the objects placed closer than 25 cm. This distance at which objects can be seen is clearly, is called the least distance of distinct vision or the near point of the eye.

Answer 2

Dear Student,

◆ Normal eye is not able to see clearly the objects placed closer than 25 cm because -

- Human eye have power of accommodation by which it can adjust focal length of lens according to distance.

- But as ciliary muscles can't contract beyond certain limit, we can't see less than 25 cm.

- This is called distance of distinct vision of the eye.

Thanks dear. Hope this helps you...