If the distance between object and its two times magnified virtual image produced by a curved mirror is 15 cm, the focal length of the mirror must be: (a) -10 cm (b) -12 cm (c) 15 cm (d) 10/3 cm

Answer: (a). Magnified virtual image: concave mirror, u = -x, v = +2x. Object-image distance x + 2x = 15 ⇒ x = 5 cm, v = +10 cm 1/f = 1/10 - 1/5 = -1/10 ⇒ f = -10 cm So the answer is (a) -10 cm.

If the distance between object and its two times magnified virtual… | JEE Main 2024 (29 Jan, Shift 2)

Q19JEE Main 2024 · 29 JAN · SHIFT 2Medium

Reflection & Mirrors

If the distance between object and its two times magnified virtual image produced by a curved mirror is $15\text{ cm}$ , the focal length of the mirror must be:

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Answer: (a)

Magnified virtual image: concave mirror, $u = -x$ , $v = +2x$ .
Object-image distance $x + 2x = 15 \Rightarrow x = 5\text{ cm}$ , $v = +10\text{ cm}$
$\frac{1}{f} = \frac{1}{10} - \frac{1}{5} = -\frac{1}{10} \Rightarrow f = -10\text{ cm}$
So the answer is (a) $-10$ cm.

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