Question

List two main causes of a person developing near sightedness. Show with the help of a ray diagram how this defect can be corrected.

Answer 1

Answer:

The defect of eye called myopia [ Short - sightedness ] is caused due to : (i) Due to high converging power of eye-lens ( because of its short focal length ) . (ii) Due to eye-ball being too long . → Myopia is corrected by using spectacles containing concave lenses .

Answer 2

Explanation:

We can start:-

Myopia is also called as Short - sightedness .

→ Myopia is that defect of vision due to which a person cannot see the distant object clearly.

→ It means that he can see the nearby objects clearly .

→ The defect of eye called myopia [ Short - sightedness ] is caused due to : 

• (i) Due to high converging power of eye-lens ( because of its short focal length ) .

• (ii) Due to eye-ball being too long .

• → Myopia is corrected by using spectacles containing concave lenses .

Note :-

• The far point of an eye suffering from myopia is less than infinity.

• The concave lens used for correcting myopia should be of such a focal length that it produce a virtual image of the distant object and the far point of the myopic eye.

• The whole purpose of using a concave lens is used to reduce the converging power of eye-lens

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