Question

A person is unable to see distinctly the objects closer than 1 m. Name the defect of vision he is suffering from. Draw ray diagrams to illustrate the cause of the defect and its correction by suitable lens.

Answer 1

The name of the defect, the person is suffering from, is hypermetropia (long sightedness) because for a hypermetropic eye, the near point shifts away from the eye. The near point of the given person is 1 m.

Hypermetropia is caused due to

1) reduction in the curvature of the lens

2) decrease in the size of the eyeball

Since a convex lens has the ability to converge the incoming rays, it can be used to correct this defect of vision. The ray diagram for the corrective measure for a hypermetropic eye is shown in the given figure.