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Question: Answered & Verified by Expert
Which of the following statement is NOT correct?
PhysicsCommunication SystemJEE MainJEE Main 2013 (23 Apr Online)
Options:
  • A
    Ground wave signals are more stable than the sky wave signals.
  • B
    The critical frequency of an ionospheric layer is the highest frequency that will be reflected back by the layer when it is vertically incident.
  • C
    Electromagnetic waves of frequencies higher than about $30 \mathrm{MHz}$ cannot penetrate the ionosphere.
  • D
    Sky wave signals in the broadcast frequency range are stronger at night than in the day time.
Solution:
2766 Upvotes Verified Answer
The correct answer is:
Electromagnetic waves of frequencies higher than about $30 \mathrm{MHz}$ cannot penetrate the ionosphere.
Above critical frequency $\left(f_c\right)$, an electromagnetic wave penetrates the ionosphere and is not reflected by it.

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