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CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2010

  • question_answer
    A plano-convex lens is made of refractive index of 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is

    A) 400 cm

    B)   200 cm

    C)   100 cm                 

    D)   50 cm

    Correct Answer: C

    Solution :

      Here, \[\frac{1}{f}=(\mu -1)\left[ \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right]\]                 \[\frac{1}{f}=(1.6-1)\left[ \frac{1}{60}-\frac{1}{\infty } \right]=\frac{1}{100}\] \[\Rightarrow \]               \[f=100\,\,cm\]


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