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BCECE Engineering BCECE Engineering Solved Paper-2005

  • question_answer
    A convex lens of focal length 10 cm and image formed by it, is at least distance of distinct vision then the magnifying power is:

    A)  3.5                                        

    B)         2.5

    C)         1.5                                        

    D)         1.4

    Correct Answer: A

    Solution :

    The converging lens used for magnification is called simple microscope or a magnifier. When image is formed at D, the least distance of distinct vision, then magnifying power \[M=1+\frac{D}{f}\] Given,   \[D=25\,cm,\,f=10\,cm\] \[\therefore \]  \[M=1+\frac{25}{10}=1+2.5=3.5\] Note: When image, is formed at infinity, \[M=\frac{D}{f}.\] This relation is called magnifying power for normal adjustment.


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