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  3. CEE Kerala Engineering

CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    The focal length of the lens of refractive index (\[\mu ~=1.5\])in air is 10 cm. If air is replaced by water of\[\mu ~=\frac{4}{3},\]its focal length is

    A)  20 cm                  

    B)         30 cm                  

    C)  40 cm                  

    D)         25 cm

    E)  35 cm

    Correct Answer: C

    Solution :

    \[\frac{{{f}_{w}}}{{{f}_{a}}}=\frac{\mu -1}{\frac{{{\mu }_{w}}}{{{\mu }_{a}}}-1}\] \[\frac{{{f}_{w}}}{10}=\frac{1-5-1}{1/8}\] \[{{f}_{w}}=\frac{0.5\times 10}{1/8}=40\,cm\]


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