JEE Main & Advanced Physics Communication System / संचार तंत्र Question Bank Self Evaluation Test - Communication System

  • question_answer
    Electromagnetic waves with frequencies greater than the critical frequency of ionosphere cannot be used for communication using sky wave propagation because:    

    A)     the refractive index of the ionosphere becomes very high for \[f>{{f}_{c}}\]

    B) the refractive index of the ionosphere becomes very low for \[f>{{f}_{c}}\]

    C) the refractive index of the ionosphere very high for \[f<{{f}_{c}}\]

    D) none of the above

    Correct Answer: A

    Solution :

    [a] For total internal reflection of sky waves, the refractive index of the ionosphere Should be less If \[f>{{f}_{c}},\] the refractive index will increase. By this waves will just pass without reflection taking place.


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