Question

Hey anyone plz explain me this problem. Plz help me.. I m in need it's an important question.. That's why I m rewarding 50 points.

Question :

Answer question numbers 3.1–3.4 on the basis of your

understanding of the following paragraph and the

related studied concepts.



The ciliary muscles of eye control the curvature of

the lens in the eye and hence can alter the effective

focal length of the system. When the muscles are

fully relaxed, the focal length is maximum. When the

muscles are strained the curvature of lens increases

(that means radius of curvature decreases) and focal

length decreases. For a clear vision the image must

be on retina. The image distance is therefore fixed for

clear vision and it equals the distance of retina from

eye-lens. It is about 2.5 cm for a grown-up person.

A person can theoretically have clear vision of

objects situated at any large distance from the eye.

The smallest distance at which a person can clearly

see is related to minimum possible focal length, The

ciliary muscles are most strained in this position. For

an average grown-up person minimum distance of

object should be around 25 cm.

A person suffering for eye defects uses spectacles

(Eye glass). The function of lens of spectacles is

to form the image of the objects within the range

in which person can see clearly. The image of the

spectacle-lens becomes object for eye-lens and whose

image is formed on retina.

The number of spectacle-lens used for the remedy

of eye defect is decided by the power of the lens

required and the number of spectacle-lens is equal to

the numerical value of the power of lens with sign. For

example power of lens required is +3D (converging

lens of focal length 100/3 cm) then number of lens

will be +3.


For all the calculations required you can use the

lens formula and lens maker’s formula. Assume that

the eye lens is equiconvex lens. Neglect the distance

between eye lens and the spectacle lens.


3.1 What do you mean by the ciliary muscles? [1]

Ans : The muscles which are used to the change in

the focal length of eye lens by changing radii of

curvature is known ciliary muscles. <------ This one I know

3.2 What is the minimum focal length of eye lens of a

normal person? [1]

Ans : 25/11 cm. <----- How??

3.3 What is the maximum focal length of eye lens of

normal person? [1]

Ans : 2.5 cm. <------ As per I think it's infinity but how?? plz explain..

3.4 A near-sighted man can clearly see object only up-

to a distance of 100 cm and not beyond this. What

is the number of the spectacles lens necessary for

the remedy of this defect? [1]
plz do this for me ​

Answer 1

Answer:

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