2. Solved Papers
  3. WB JEE Medical

WB JEE Medical WB JEE Medical Solved Paper-2011

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

    A)  9D                                         

    B)  2D

    C)  3D                                         

    D)  7D

    Correct Answer: A

    Solution :

                     We have the effective power given by \[{{P}_{eff}}={{P}_{1}}+{{P}_{2}}\] Also we know,   \[P=\frac{1}{f}\] Hence, \[{{P}_{eff}}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}=\frac{1}{0.20}+\frac{1}{0.25}=5+4=9D\]


You need to login to perform this action.
You will be redirected in 3 sec spinner