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RAJASTHAN PMT Rajasthan - PMT Solved Paper-2002

  • question_answer
    If prism angle\[\alpha =1{}^\circ ,\,\mu =1.54,\] distance between screen and prism \[(b)=0.7\,m,\] distance between prism and source \[a=0.3\,m,\] \[\lambda =180\pi \] nm then in Fresnal \[\] biprism find the value of P (finge width):

    A)  \[{{10}^{-4}}m\]

    B)                         \[{{10}^{-3}}mm\]

    C)  10-4\[\times \pi m\]  

    D)         \[\pi \times \]10-3m

    Correct Answer: B

    Solution :

    \[a=0.3,\alpha =1{}^\circ ,\mu =1.54\] \[d=2a(\mu -1)\alpha \] \[\begin{align}   & =2\times 0.3(1.54-1)\times 1 \\  & =2\times 0.3\times 0.54=0.324 \\ \end{align}\] Fringe width \[=\beta =\frac{D\lambda }{d}\]                                 \[=\frac{0.7\times 180\pi \times {{10}^{-9}}}{0.324}\]                                 \[=\frac{7\times 18\pi \times {{10}^{-6}}}{324}={{10}^{-3}}mm\]


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