CBSE Class 10 Science 2017 · Paper 531/1 · Question 15

Myopia (near-sightedness) is the defect of vision in which a person can see nearby objects clearly but cannot see distant objects distinctly. Its far point is nearer than infinity, and the image of a distant object is formed in front of the retina. Two causes: (i) excessive curvature of the eye lens, so that it converges light too strongly; (ii) elongation of the eyeball, so that the retina lies too far behind the eye lens. Correction: a concave (diverging) lens of suitable power, whose focal length is equal in magnitude to the distance of the far point. It spreads the parallel rays from a distant object so that they appear to come from the far point F; the eye can focus on F, so the image is now formed on the retina (see the ray diagram).