NEET Sample Paper NEET Sample Test Paper-66

  • question_answer
    The focal length of objective and eye lens of an astronomical telescope are respectively 2 m and 5 cm. Final image is formed at (i) least distance of distinct vision (ii) infinity. The magnifying power in both cases will be

    A) -48, -40            

    B) -40, -48

    C) -40, 48             

    D) -48, 40

    Correct Answer: A

    Solution :

    When the final image is at the least distance of distinct vision, then \[m=-\frac{{{f}_{o}}}{{{f}_{e}}}\,=\,\,\left( 1+\frac{{{f}_{e}}}{D} \right)\,\,=\,\,\frac{200}{5}\,\left( 1+\frac{5}{25} \right)\] \[=\,\,\frac{200\times 6}{5\times 5}\,\,=\,\,-48\] When the final image is at infinity, then \[m=\frac{-{{f}_{o}}}{{{f}_{e}}}\,\,=\,\frac{200}{5}\,\,=\,\,-40\]


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