What is myopia ? What are the reasons that arise this defect ? How can you rectify this defect ?

Explanation

Myopia (or) short sightedness : Myopia is a vision defect in which a person can see nearby objects clearly but cannot see the distant objects clearly beyond a certain point.
Cause of short sightedness (myopia) : 1) The eye ball gets elongated along its axis so that the distance between the eye lens and the retina becomes largers.
2) The focal length of the eye lens becomes too short due to the excessive curvature of cornea.
Correction of Myopia :
1) A myopia eye is corrected by using concave lens of focal length equal to the distance of the far point 'F' from the eye.
2) This lens diverges the parallel rays from distant object as if they are coming from the far point 'F'.
3) Finally the eye lens forms a clear image on the retina.