Question:

Long range radio transmission is possible when the radiowaves are reflected from the ionosphere. For this to happen the frequency of the radiowaves must be in the range :

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Sky-wave propagation by ionospheric reflection works for the HF band; VHF waves pass through the ionosphere.
Updated On: Nov 11, 2026
  • 80 - 150 MHz
  • 8 - 25 MHz
  • 1 - 3 MHz
  • 150 - 500 kHz
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The Correct Option is B

Solution and Explanation

The ionosphere reflects waves of frequency up to about 30 MHz (HF, short-wave), while waves above this (VHF and higher, e.g. 80-150 MHz) penetrate it and escape. Very low frequencies (150-500 kHz) are mostly ground waves and 1-3 MHz waves are largely absorbed in the D layer by day. Short-wave long-range communication therefore uses about 3-30 MHz; among the given ranges 8-25 MHz lies in this band.
Answer: (2) 8 - 25 MHz
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