JEE Main · 2019 · 09 Apr 2019 · Shift 1 · Geometrical Optics

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A concave mirror for face viewing has focal length of 0.4 m . The distance at which you hold the mirror from your face in order to see your image upright with a magnification of 5 is:

(A)0.16 m
(B)1.60 m
(C)0.24 m
(D)0.32 m✓ Correct

Answer: (D)

Solution

A face-viewing concave mirror gives an upright, magnified virtual image, so we use

m = \frac{f}{f - u}

with

f = - 40

cm. Setting

m = 5

gives

5 = \frac{- 40}{- 40 - u}

, so

- 40 - u = - 8

and

u = - 32

cm. The mirror is held

0.32

m from the face.

JEE Main · 2019 · 09 Apr 2019 · Shift 1 · Single correct option

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