What is hypermetropia? Give its two causes. With ray diagrams, show the defect and how it is corrected.

1. 1 · Define in one line. Hypermetropia (far-sightedness) is the defect in which distant objects are seen clearly but nearby objects are not. The near point moves beyond 25 cm.
2. 2 · Give two causes.
   • The focal length of the eye lens is too long.
   • The eyeball has become too small.
3. 3 · Draw the near point and the defect. [Figures: (a) near point N of this eye, farther than the normal near point N′ at 25 cm; (b) rays from N′ meeting behind the retina]
4. 4 · Draw the correction. [Figure (c): convex lens in front of the eye; rays from N′ bend and seem to come from N; they now meet on the retina]
5. 5 · Explain the correction. A convex lens of suitable power adds converging power, so the image of a near object forms on the retina.
6. 6 · Daily-life link. People with this defect use convex reading glasses. An eye test gives the exact power in dioptres, with a plus sign.
7. 7 · Close in one line. So hypermetropia is corrected with a convex lens, which has positive power.

Scoring tip: Draw all three figures (near point, defect, correction) and label N, N′ and the retina. Many students skip figure (a) and lose a mark.