JEE Main & Advanced Physics EM Waves Question Bank Self Evaluation Test - Electromagnetic Waves

  • question_answer
    For wave propagation of a \[10\text{ }MHz\] signal, what should be the maximum electron density in ionosphere

    A) \[\tilde{\ }1.2\times {{10}^{12}}{{m}^{-3}}\]

    B) \[\tilde{\ }{{10}^{6}}{{m}^{-3}}\]

    C) \[\tilde{\ }{{10}^{14}}{{m}^{-3}}\]

    D) \[\tilde{\ }{{10}^{22}}{{m}^{-3}}\]

    Correct Answer: A

    Solution :

    [a] If maximum electron density of the ionosphere is \[{{N}_{\max }}\] per \[{{m}^{3}}\] then the critical frequency \[{{f}_{c}}\] is given by \[{{f}_{c}}=9({{N}_{\max }})1/2\] \[\Rightarrow \,\,10\times {{10}^{6}}=9{{(N)}^{1/2}}\Rightarrow N=1.2\times {{10}^{12}}{{m}^{-3}}\]


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