Manipal Medical Manipal Medical Solved Paper-2003

  • question_answer
    For achromatic combination of lenses, if we use two lenses of focal length and\[f\] respectively, dispersive powers\[\omega \]and\[\omega ,\]then:

    A)  \[\omega ={{\omega }_{0}},\omega =2{{\omega }_{0}},f=2f\]

    B)  \[\omega ={{\omega }_{0}},\omega =2{{\omega }_{0}},f=-2f\]

    C)  \[\omega ={{\omega }_{0}},\omega =2{{\omega }_{0}},f=f/2\]

    D)  \[\omega ={{\omega }_{0}},\omega =2{{\omega }_{0}},f=-f/2\]

    Correct Answer: B

    Solution :

     The condition of achromatic combination is \[\frac{\omega }{\omega }=-\frac{f}{f}\] This is satisfied if \[\omega ={{\omega }_{0}},\omega =2{{\omega }_{0}}\]and\[f=2f\] So that, \[\frac{{{\omega }_{0}}}{2{{\omega }_{0}}}=\frac{-f}{-2f}\] \[\Rightarrow \] \[\frac{1}{2}=\frac{1}{2}\]


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