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NEET Sample Paper NEET Sample Test Paper-81

  • question_answer
    In an equal convex lens having radius of curvature R and focal length f. If \[f\,\,>\,\,R\], the refractive index \[\mu \] of the material of lens is

    A)  \[0 < \mu  < 1\]                       

    B)  \[1 < \mu  < 1.5\]

    C)  \[\mu  > 2\]                 

    D)  None of these

    Correct Answer: B

    Solution :

    As, \[\frac{1}{f}=(\mu -1)\left( \frac{2}{R} \right)\,for\,\,equiconvex\,\,lens\] \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,f=\frac{R}{2\left( \mu -1 \right)}\] As,           \[\operatorname{f} > R\] \[\Rightarrow \,\,\,\,\,\frac{R}{2(\mu -1)}>R\,\,\,\Rightarrow \,\,\,\frac{1}{2(\mu -1)}\,\,>\,\,1\] \[\Rightarrow \,\,\,\,\,2(\mu -1)<1\] \[\Rightarrow \,\,\,\,\,\,\,\,\mu -1<\frac{1}{2}\,\,\,\Rightarrow \,\,\,\mu <1+\frac{1}{2}\,\,\,\Rightarrow \,\,\,\mu \,\,<\,\,1.5\]


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