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JEE Main & Advanced Physics Ray Optics Question Bank Refraction at Curved Surface

  • question_answer
    A convex lens of focal length \[f\] is placed somewhere in between an object and a screen. The distance between the object and the screen is \[x\]. If the numerical value of the magnification produced by the lens is \[m,\], then the focal length of the lens is

    A)            \[\frac{mx}{{{(m+1)}^{2}}}\]

    B)            \[\frac{mx}{{{(m-1)}^{2}}}\]

    C)            \[\frac{{{(m+1)}^{2}}}{m}x\]

    D)            \[\frac{{{(m-1)}^{2}}}{m}x\]

    Correct Answer: A

    Solution :

                       \[\frac{v}{-u}=-m\,\,\text{and}\,\text{ }v+u=x\Rightarrow u=\frac{x}{1+m}\]            \[\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\Rightarrow f=\frac{mx}{{{(m+1)}^{2}}}\].


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