Topic: Magnification, power of lens, combination of thin lenses· Optics

A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use, will be

1. concave, -0.25 diopter

2. concave, -0.2 diopter

3. convex, +0.15 diopter

4. convex, +2.25 diopter

Doubtly Asked 30 Oct 2026 NEET UG 2016 Phase 2 neet Save WhatsApp Report

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Answer: 1. concave, -0.25 diopter

The person's far point is 400 cm; to see infinity the lens must form the image of a distant object at 400 cm. Such a lens is diverging (concave) with $f=-400$ cm.

$$P=\frac1f=\frac{1}{-4\ \text{m}}=-0.25\ \text{D}$$

Option (1). A convex lens is for farsightedness, not this case.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use, will be

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