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Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2005

  • question_answer
    In a concave mirror experiment, an object is placed at a distance\[{{x}_{1}}\] from the focus and the image is formed at a distance \[{{x}_{2}}\] from the focus. The focal length of the mirror would be

    A)  \[{{x}_{1}}{{x}_{2}}\]                                    

    B)  \[\sqrt{{{x}_{1}}{{x}_{2}}}\]

    C)  \[\sqrt{{{x}_{1}}/{{x}_{2}}}\]                                     

    D) \[\frac{{{x}_{1}}+{{x}_{2}}}{2}\]

    Correct Answer: B

    Solution :

    According to Newton's formula \[{{f}_{1}}{{f}_{2}}={{x}_{1}}{{x}_{2}}.\] But         \[{{f}_{1}}={{f}_{2}}=f\] \[\therefore \]  \[{{f}^{2}}={{x}_{1}}{{x}_{2}}\] or            \[f=\sqrt{{{x}_{1}}{{x}_{2}}}\]


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