Question

A boy reads book from 25 cm distance ( minimum distance of distinct vision ),than

Answer 1

Answer:

the minimum distance of distinct vision of human eye is 25cm

Answer 2

(2) Focal length of eye lens is minimum and ciliary  muscles are relaxed

Probably the complete question is: ......then

1) Eye lens becomes thin and ciliary muscles are  contracted

(2) Focal length of eye lens is minimum and ciliary  muscles are relaxed

(3 Focal length of eye lens is minimum and ciliary  muscles are maximum contract

ed

(4) Focal length of eye lens is maximum and ciliary

muscles are relaxed  focal length​

Explanation:

The minimum natural distance for a human eye vision is 25 cm at which the lens of the eye has its natural focal length without any strain in the ciliary muscles, i.e. the ciliary muscles are neither stretched nor contracted.

Ciliary muscles are the radially attached muscles around the lens of the human eye which are responsible for the change in the focal length of the eye-lens (by expanding and contracting).

• When the ciliary muscles are stretched the lens also stretches and becomes thin (imagine a flexible convex lens) and hence the lens becomes less bulged therefore converges the light at a farther distance increasing the focal length. The vice-versa happens in case of reducing the focal length.

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