RAJASTHAN PMT Rajasthan - PMT Solved Paper-2001

  • question_answer
    Power of combination of two lens of focal lengths 20 cm and 25 cm respectively:

    A)  +1D                                      

    B)  +9D

    C)  -1D                       

    D)         -9D

    Correct Answer: B

    Solution :

    Power of first lens \[{{P}_{1}}=\frac{100}{{{f}_{1}}}=5D\] Power of second lens \[{{P}_{1}}=\frac{100}{{{f}_{1}}}=\frac{100}{20}\,=5D\] Total power \[P={{P}_{1}}+{{P}_{2}}=5+4=9\,D\]


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