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JEE Main & Advanced Physics Ray Optics Question Bank Refraction at Curved Surface

  • question_answer
    A glass convex lens \[({{\mu }_{g}}=1.5)\] has a focal length of \[8\,cm\] when placed in air. What would be the focal length of the lens when it is immersed in water ( \[{{\mu }_{w}}=1.33\])  [BHU 1994; MP PMT 1996]

    A)            2 m                                           

    B)            4 cm

    C)            16 cm                                      

    D)            32 cm

    Correct Answer: D

    Solution :

               \[\frac{{{f}_{l}}}{{{f}_{a}}}=\frac{{{(}_{a}}{{\mu }_{g}}-1)}{{{(}_{l}}{{\mu }_{g}}-1)}\]\[\frac{\sin {{45}^{o}}}{\sin {{30}^{o}}}\]\[\Rightarrow {{f}_{w}}=32\,cm\]


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