Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2008

  • question_answer
    The frequency of a light wave in a material is \[2\times {{10}^{14}}\]Hz and wavelength is \[5000\,\,\overset{\text{o}}{\mathop{\text{A}}}\,\]. The refractive index of material will be

    A)  1:40                                      

    B)  1.50

    C)  3.00                                      

    D)  1.33

    Correct Answer: C

    Solution :

    Velocity of light waves in material is \[v=v\lambda \]                       ... (i) Refractive index of material is                 \[\mu =\frac{c}{v}\]                         ?.(ii) where c is speed of light in vacuum or air. or             \[\mu =\frac{c}{v\lambda }\]              ?..(iii) Given,     \[v=2\times {{10}^{14}}Hz,\]                 \[\lambda =5000\overset{\text{o}}{\mathop{\text{A}}}\,=5000\times {{10}^{-10}}m,\]                 \[c=3\times {{10}^{5}}m/s\] Hence, from Eq. (iii), we get                 \[\mu =\frac{3\times {{10}^{8}}}{2\times {{10}^{14}}\times 5000\times {{10}^{-10}}}=3.00\]


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