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JEE Main 2026 (24 Jan, Shift 2) · Reflection & Mirrors

Reflection & Mirrors question from JEE Main 2026 (24 Jan, Shift 2)

Q4JEE Main 2026 · 24 JAN · SHIFT 2Medium

Reflection & Mirrors

Distance between an object and three times magnified real image is 40 cm. The focal length of the mirror used is ______ cm.

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Answer: (d)

  1. Real image three times magnified: m=−3⇒v=3um = -3 \Rightarrow v = 3u (both in front of the mirror).
  2. Object-image distance =∣v−u∣=2∣u∣=40⇒u=−20 cm= |v - u| = 2|u| = 40 \Rightarrow u = -20\text{ cm}, v=−60 cmv = -60\text{ cm}
  3. 1f=1v+1u=−160−120=−115\frac{1}{f} = \frac{1}{v} + \frac{1}{u} = -\frac{1}{60} - \frac{1}{20} = -\frac{1}{15}
  4. f=−15 cmf = -15\text{ cm}, so the answer is (d).
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