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10th Class Science Light - Reflection and Refraction Question Bank Light - Reflection and Refraction

  • question_answer
    A converging lens magnifies a real image to four times its original size. Given that the focal length of the converging lens is 20 cm. what is the object distance?

    A) 5 cm                                     

    B) 25 cm                  

    C) 40 cm                                   

    D) 100 cm

    Correct Answer: B

    Solution :

    By using the lens equation, \[\frac{1}{u}+\frac{1}{v}=\frac{1}{f}\]   \[\frac{1}{u}+\frac{1}{4u}=\frac{1}{20},\frac{5}{4u}=\frac{1}{20},u=25\,cm\]


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