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RAJASTHAN PMT Rajasthan - PMT Solved Paper-1996

  • question_answer
    The radius of fourth half period zone at a point 4 m away from a plane wave front of wavelength \[6400\overset{\text{o}}{\mathop{\text{A}}}\,\]is:

    A)  \[32\times {{10}^{-4}}m\]                          

    B)  \[30\times {{10}^{-4}}cm\]        

    C)         \[33\times {{10}^{-4}}mm\]      

    D)         \[16\times {{10}^{-3}}m\]

    Correct Answer: A

    Solution :

    Radius of half period zone \[{{r}_{n}}=\sqrt{dn\,\lambda }\]                 \[\therefore \]  \[{{r}_{4}}=\sqrt{9\times 4\times 6400\times {{10}^{-10}}}\]                                 \[=32\times {{10}^{-4}}m\]


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