CBSE Class 10 Science 2017 · Paper 531/2 · Question 15

Hypermetropia (far-sightedness) is the defect of vision in which a person can see distant objects clearly but cannot see nearby objects distinctly. The near point of the eye lies farther away than the normal near point (25 cm): light from a nearby object would be focussed at a point behind the retina. Two causes: (i) the focal length of the eye lens is too long; (ii) the eyeball has become too small. Correction: a convex (converging) lens of suitable power. As the ray diagram shows, rays from an object at the normal near point N (25 cm) are refracted by the convex lens so that they appear to come from N′, the near point of the defective eye; the eye can focus N′, so the image is formed on the retina.