A plano convex lens of $\left( {f = 20\,\,{\rm{cm}}} \right)$ is silvered at plane surface. New $f$ will be

JEE PHYSICS MCQ: RAY OPTICS

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A plano convex lens of

\left( {f = 20\,\,\mathrm{cm}} \right)

is silvered at plane surface. New

f

will be

View answer and explanation

Correct option: C

\mathrm{30}\,\,\mathrm{cm}

The correct answer is not among the options provided. The correct focal length should be 10 cm. Option D (

\mathrm{10}\,\mathrm{cm}

) is the closest to the correct answer, but the provided explanation in the original response is incorrect. The correct answer is obtained by considering the lens-mirror combination.

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