List two causes leading to myopia of the eye. Draw ray diagrams to show the image formation in case of a defective eye and a corrected eye.

(N/A) The two main causes of myopia are:
$(i)$ Excessive curvature of the eye lens (decrease in focal length).
$(ii)$ Elongation of the eyeball.
In myopia,the image of a distant object is formed in front of the retina instead of on the retina itself. This defect is corrected by using a concave lens of suitable power,which diverges the incoming light rays so that the image is formed on the retina.