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Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2006

  • question_answer
    The focal lengths of the objective and eye-piece of a telescope are respectively 100 cm and 2cm. The moon substends an angle of \[0.5{}^\circ \] at the eye. If it is looked through the telescope, the angle subtended by the moon's image will be

    A) \[100{}^\circ \]

    B) \[50{}^\circ \]

    C) \[25{}^\circ \]

    D) \[10{}^\circ \]

    Correct Answer: C

    Solution :

    Given,   \[{{f}_{o}}=100cm,\] \[{{f}_{e}}=2cm\] Visual angle subtended by moon \[(\alpha )={{0.5}^{o}}\] Visual angle subtended at eye with moon's image \[(\beta )=?\] Magnifying power of telescope \[(M)=\frac{\beta }{\alpha }=\frac{{{f}_{o}}}{{{f}_{e}}}\] \[\therefore \]  \[\beta =\alpha .\,\frac{{{f}_{o}}}{{{f}_{e}}}=0.5\times \frac{100}{2}={{25}^{o}}\]


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