In corrective eyewear for farsightedness, which lens is used?

• A. Plane lens
• B. Concave lens
• C. Plano lens
• D. Convex lens

Answer: (D)

The main idea is that corrective lenses for farsightedness must move the eye’s focal point forward so images land on the retina. Farsighted people have trouble focusing close because light rays are focused behind the retina. A convex lens, which is thicker in the middle, bends parallel rays toward each other so they converge sooner. This makes near objects focus on the retina, improving clarity. A plane lens has no refractive power and wouldn’t change the focus, while a concave (diverging) lens spreads light apart, making near vision worse. A plano lens also provides no correction. So the lens used for farsightedness is convex.