Which of the following is used for the correction of short sightedness?

1. Analyze the question Short sightedness (myopia) is a defect of the eye. You are asked which optical device corrects it.

2. Explain the concept

• In a short-sighted eye, a person sees near objects clearly but distant objects look blurred.
• The cause is that the eyeball is too long, or the eye lens is too strongly converging. Light from distant objects is focused in front of the retina instead of on it.
• To fix this, the light must be spread out (diverged) a little before it enters the eye, so the eye lens can focus it exactly on the retina.
• A diverging lens, which is a concave lens, does this job.

(For comparison, long sightedness, or hypermetropia, is corrected with a convex (converging) lens.)

3. Step-by-step solution

1. Defect: short sightedness, so the image forms in front of the retina.
2. Needed correction: diverge the rays so the image moves back onto the retina.
3. Device that diverges light: concave lens.
4. Mirrors are not worn to correct vision, so options C and D are out.
5. Convex lens (A) converges light and would make the problem worse.

4. Answer The correct option is B. concave lens.

5. Exam tip Remember: "Myopia = Minus lens = Make it spread (concave)." Short sight uses a concave (negative power) lens. Long sight uses a convex (positive power) lens.