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  3. WB JEE Medical

WB JEE Medical WB JEE Medical Solved Paper-2007

  • question_answer
    Two thin lenses of focal length 20 cm and 25 cm are in contact. The effective power of the combination is

    A)  4.5 D                                    

    B)  18 D

    C)  45 D                                     

    D)  9 D

    Correct Answer: D

    Solution :

                     \[{{P}_{1}}=\frac{100}{20}=5D,{{P}_{2}}=\frac{100}{25}=4D\] Effective power \[P={{P}_{1}}+{{P}_{2}}\]                                 \[=5+4\]                                 \[=9D\]


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