JEE Main & Advanced Sample Paper JEE Main - Mock Test - 4

  • question_answer
    In optical communication system operating at \[1200\text{ }nm,\] only \[2%\] of the source frequency is available for TV transmission having a bandwidth of\[5\text{ }MHz\]. The number of TV channels that can be transmitted is

    A) 2 million            

    B) 10 million

    C) \[0.1\] million         

    D) 1 million

    Correct Answer: D

    Solution :

    Optical source frequency \[\text{v=}\frac{c}{\lambda }\] \[\Rightarrow \,\,\,\text{v=}\frac{3\times {{10}^{8}}m{{s}^{-1}}}{1200\times {{10}^{-9}}m}=2.5\times {{10}^{14}}Hz\]
    Bandwidth of channel (\[2%\]of the source frequency) \[=5\times {{10}^{12}}Hz\]
    Number of channels \[=\frac{\text{Total band}\,\text{width}}{\text{ }\!\!~\!\!\text{ Bandwidth needed per channel}}\]\[=\frac{5\times {{10}^{12}}Hz}{5\times {{10}^{16}}Hz}={{10}^{6}}=1\,million\]


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