Give scientific reasons for the following statements:
To rectify the defect of near-sightedness or myopia, concave lens of suitable focal length is used as corrective lens.

Explanation

The eye lens of a person having defect of near-sightedness or myopia, does not become thin as per the requirement and so the rays after being refracted by the eye lens get focussed at a position short of retina. So distant objects cannot be seen clearly.
If a person having defect of near-sightedness, uses concave lens of suitable focal length, then light rays become slightly divergent. Hence, the image can be formed on retina.
Thus, if the image is formed on retina, then the distant object may be seen clearly.