CBSE Class 10 Science 2019 · Paper 31/3/1 · Question 13(b)

(i) A student is considered myopic (near-sighted) when the student can see nearby objects, such as the notebook, clearly but cannot see distinctly the words written on the blackboard: the far point of the eye has come nearer than infinity, so the image of a distant object forms in front of the retina. (ii) Causes: (1) excessive curvature of the eye lens (or of the cornea at the front of the eyeball); (2) elongation of the eyeball. (iii) The defect is corrected with spectacles having a concave (diverging) lens of suitable power, whose focal length equals the distance of the far point. Ray diagram: parallel rays from a distant object fall on the concave lens and diverge as if they came from the far point F; the eye lens then converges them to form the image on the retina (without the lens they would meet in front of the retina).