NEET Physics Lenses MCQ Question
An equiconvex lens of refractive index 1.5 is placed in contact with a liquid of unknown refractive index over a plane mirror. A small needle placed along the principal axis has its inverted image at the same position as the needle itself, 45 cm from the lens. When the liquid is removed, this distance reduces to 30 cm. What is the refractive index of the liquid?
33
40
45
50
Correct Answer
Detailed Explanation
The inverted image coinciding with the needle position indicates that the lens-liquid system behaves like a plane mirror. Using the lens formula and given distances, the refractive index of the liquid can be calculated as 1.33.
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