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Punjab Medical Punjab - MET Solved Paper-1999

  • question_answer
    A plane convex lens is made of refractive index\[1.6\]. The radius of curvature of the curved surface is\[60\,\,cm\]. Then, the focal length of the lens will be

    A) \[400\,\,cm\]                    

    B) \[200\,\,cm\]

    C) \[100\,\,cm\]                    

    D) \[50\,\,cm\]

    Correct Answer: C

    Solution :

    Refractive index\[\mu =1.6\] Radius of curved surface\[{{R}_{1}}=60\] Radius of plane surface\[{{R}_{2}}=\infty \] The relation for focal length\[n\]                 \[\frac{1}{f}=(\mu -1)\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\]                     \[=(1.6-1)\left( \frac{1}{60}-\frac{1}{\infty } \right)\]                     \[=0.6\times \frac{1}{60}=0.01\] or            \[f=\frac{1}{0.01}=100\,\,cm\]


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