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NEET NEET SOLVED PAPER 2016 Phase-I

  • question_answer
    A astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance :-

    A)  37.3 cm                               

    B)  46.0 cm

    C)  50.0 cm                               

    D)  54.0 cm

    Correct Answer: D

    Solution :

                     Using lens formula for objective lens                 \[\frac{1}{{{v}_{0}}}-\frac{1}{{{u}_{0}}}=\frac{1}{{{f}_{0}}}\Rightarrow \frac{1}{{{v}_{0}}}=\frac{1}{{{f}_{0}}}+\frac{1}{{{u}_{0}}}\]                 \[\Rightarrow \] \[\frac{1}{{{v}_{0}}}=\frac{1}{40}+\frac{1}{-200}=\frac{+5-1}{200}\] \[\Rightarrow \]\[{{v}_{0}}=50\,cm\] Tube length \[\ell =\,|{{v}_{0}}|+{{f}_{e}}=50+4=54\,cm.\]


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