JEE Main · 2023 · 30 Jan 2023 · Shift 1 · Geometrical Optics

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A person has been using spectacles of power- 1.0 diopter for distant vision and a separate reading glass of power 2.0 diopters. What is the least distance of distinct vision for this person:

(A)10 cm
(B)40 cm
(C)30 cm
(D)50 cm✓ Correct

Answer: (D)

Solution

The reading glass has power

+ 2 D

, i.e. focal length

0.5 m

. When a page is held at the standard near distance of

25 cm

, this lens forms a virtual image at the person's own near point:

\frac{1}{v} = P + \frac{1}{u} = 2 + \frac{1}{- 0.25} = - 2 m^{- 1}

, so

v = - 0.5 m

. The least distance of distinct vision for this person is

50 cm

JEE Main · 2023 · 30 Jan 2023 · Shift 1 · Single correct option

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