NEET Sample Paper NEET Sample Test Paper-21

  • question_answer A double convex lens of focal length 6 cm is made of glass of refractive index 1.5. The radius of curvature of one surface is double that of the other surface. The value of smaller radius of curvature is:

    A)  6 cm             

    B)  4.5 cm

    C)    9 cm             

    D)    4 cm              

    Correct Answer: B

    Solution :

    \[\frac{1}{f}=(\mu -1)\left\{ \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{1}}} \right\}\]or \[\frac{1}{6}(1.5-1)\left\{ \frac{1}{R}+\frac{1}{2R} \right\}\] \[\Rightarrow \]\[R=4.5\,cm.\] Hence, the correction option is (b).

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