NEET Sample Paper NEET Sample Test Paper-50

  • question_answer The central fringe of the interference pattern produced by light of wavelength 6000 A is found to shift to the position of 4th bright fringe after a glass plate of refractive index 1.5 is introduced. The thickness of the glass plate would be-                                  

    A) \[4.8\,\mu m\]               

    B) \[8.23\,\mu m\]

    C) \[14.98\,\mu m\]                        

    D) \[3.78\,\mu m\]

    Correct Answer: A

    Solution :

    \[\Delta x=\frac{dy}{D}\,\,-\,\,(\mu -1)\,t=0\] \[y=(\mu -1)\,\,\frac{tD}{d}\] \[4\beta =(\mu -1)\frac{tD}{d}\,\,\Rightarrow \,\,4\lambda =(\mu -1)\,t\] \[t=\left( \frac{4\lambda }{\mu -1} \right)\,\,=\,\,\frac{4\times 6000\times {{10}^{-10}}}{1.5-1}\] \[t\,\,=\,\,4.8\,\,\times \,\,{{10}^{-6}}\] \[t\,\,=\,\,4.8\,\mu m\]


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