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JEE Main & Advanced Physics Ray Optics Question Bank Mock Test - Geometrical Optics

  • question_answer
    Consider an equiconvex lens of radius of curvature R and focal length\[f.\,\]If \[f>R\,\], the refractive index \[\mu \]of the material of the lens

    A) Is greater than zero but less than 1.5

    B) Is greater than 1.5 but less than 2.0

    C) Is greater than 1.0 but less than 1.5

    D) None of these

    Correct Answer: C

    Solution :

    [c] \[\frac{1}{f}=(\mu -1)\left( \frac{2}{R} \right)\] Or \[f=\frac{R}{2(\mu -1)}\] Now, \[f>R\] \[\therefore \frac{R}{2(\mu -1)}>R\] Or \[\frac{1}{2(\mu -1)}>1\] or \[2(\mu -1)<1\] Or \[\mu -1<\frac{1}{2}\] or \[\mu <\left( 1+\frac{1}{2} \right)\]or \[\mu <1.5\]


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