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JEE Main & Advanced Physics Ray Optics Question Bank Self Evaluation Test - Ray Optics and Optical Instruments

  • question_answer
    The given lens is broken into A four parts and rearranged as shown. If the initial focal length is/then after rearrangement the equivalent focal length is-

    A) f

    B) f/2  

    C) f/4

    D) 4f

    Correct Answer: B

    Solution :

    [b] Cutting a lens in transverse direction doubles their focal length i.e. 2f. Using the formula of equivalent focal length, \[\frac{1}{f}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}+\frac{1}{{{f}_{3}}}+\frac{1}{{{f}_{4}}}\] We get equivalent focal length as f/2.


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