JEE Main & Advanced Physics Ray Optics JEE PYQ-Ray Optics

  • question_answer
    If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5 mm, the focal length of the eye-piece, should be close to [JEE MAIN Held on 07-01-2020 Morning]

    A) 2 mm

    B) 33 mm

    C) 22 mm

    D) 12 mm

    Correct Answer: C

    Solution :

    [c] \[m\simeq \frac{L}{{{f}_{0}}}\left( 1+\frac{D}{{{f}_{e}}} \right)\]
                \[\Rightarrow 375=\frac{150}{5}\left( 1+\frac{250}{{{f}_{e}}} \right)\]
                \[\Rightarrow 12.5=1+\frac{250}{{{f}_{e}}}\]
                \[\Rightarrow {{f}_{e}}=\frac{250}{11.5}=21.7\]
                \[\Rightarrow \]


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