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  3. RAJASTHAN PMT

RAJASTHAN PMT Rajasthan - PMT Solved Paper-1997

  • question_answer
    Two lenses of power + 2.5 D and - 3.75 D are placed in contact to form compound lens. What will be the focal length of compound lens?

    A)  - 20 cm                

    B)         - 40 cm

    C)         - 60 cm                

    D)         - 80 cm

    Correct Answer: D

    Solution :

    Power of combination \[P={{P}_{1}}+{{P}_{2}}\] \[=2.5-3.75=-1.25\] Focal length \[F=\frac{1}{P}\]                 \[=\frac{1}{1.25}=-\frac{4}{5}m\]                 \[=-80cm\]


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