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JEE Main & Advanced Physics Ray Optics Question Bank Self Evaluation Test - Ray Optics and Optical Instruments

  • question_answer
    Convex surface of thin concavo-convex lens of refractive index 1.5 is silvered as shown. A small object is kept in air at 30 cm left of the lens on its principal axis. The distance of the final image is

    A) 20cm

    B) 30cm

    C) 10cm

    D) 15cm

    Correct Answer: C

    Solution :

    [c] Power of combinations \[P=2\left( \mu -1 \right)\left( \frac{1}{-60}-\frac{1}{-20} \right)+\left( \frac{-1}{-20/2} \right)\] \[P=\frac{2}{15}=\frac{-1}{f}\] \[\therefore \]Resultant focal length\[f=-\frac{15}{2}\] \[\therefore \]From mirror formula\[\frac{1}{-30}+\frac{1}{v}=\frac{1}{f}\] Solving \[v=-10\text{ }cm.\]


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