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

  • question_answer
    A concave mirror forms the real image of an object which is magnified 4 times. The object is moved 3 cm away, the magnification of the image is 3 times/What is the focal length of the mirror?

    A)  3 cm                     

    B)         4 cm

    C)  12 cm                  

    D)         36 cm  

    Correct Answer: D

    Solution :

     For mirrors\[u=\frac{f(m-1)}{m}\] In first case,\[u=\frac{f(-4-1)}{-4}\] In the second case,\[u+3=\frac{f(-3-1)}{-3}\] On solving, we get    \[f=36\,\,cm\]


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