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RAJASTHAN PMT Rajasthan - PMT Solved Paper-1997

  • question_answer
    A compound lens is formed by combining one convex and one concave lens of same focal length 20 cm. This compound lens is used to see a 5 cm high object situated at a distance of 20 cm. Image will be:

    A)  enlarged and reverse

    B)  small and erect

    C)  errect and same size of object

    D)  reverse and same size of object

    Correct Answer: C

    Solution :

    Equivalent focal length of combination \[\frac{1}{F}=\frac{1}{{{F}_{1}}}=\frac{1}{{{F}_{2}}}=\frac{1}{20}-\frac{1}{20}=0\] \[F=\infty \] Combination will behave as a plane mirror, size of image will be equal to size of object.


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