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AMU Medical AMU Solved Paper-2001

  • question_answer
    The refractive indices of the material of a lens for violet and red colours are respectively 1.56 and 1.54. If the focal length of the lens for violet light is 40 cm, then focal length for red colour is

    A)  41.48 cm                            

    B)  20.25 cm

    C)  15.3 cm                               

    D)  2.8 cm

    Correct Answer: A

    Solution :

                     The focal length for red colour is                 \[{{f}_{R}}={{f}_{V}}=\frac{({{\mu }_{V}}-1)}{({{\mu }_{R}}-1)}\] Given,   \[{{f}_{V}}=40\,cm,\,\,{{\mu }_{V}}=1.56,\,\,{{\mu }_{R}}=1.54\] \[\therefore \]  \[{{f}_{R}}=40\times \frac{0.56}{0.54}=41.48\,cm\]


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