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NEET 2000 (AIPMT) · Combination of Lenses

Combination of Lenses question from NEET 2000 (AIPMT)

Q80NEET 2000 · AIPMTMedium

Combination of Lenses

For a plano convex lens (μ\mu = 1.5) has radius of curvature 10 cm. It is silvered on its plane surface. Find focal length after silvering

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Answer: (a)

  1. Lens: fl=Rμ−1=100.5=20 cmf_l = \frac{R}{\mu - 1} = \frac{10}{0.5} = 20\text{ cm}; plane mirror has Pm=0P_m = 0.
  2. Silvered lens: P=2Pl+Pm=220P = 2P_l + P_m = \frac{2}{20}
  3. F=10 cmF = 10\text{ cm}
  4. So the answer is (a) 10 cm.
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