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प्रश्न
Explain why this mode cannot be used for long distance communication using high frequencies.
उत्तर
Ground waves are the radio waves that travel along the surface of the Earth. In ground wave propagation, a large portion of wave energy is in space near the surface of the Earth. The propagation of the wave is guided along the Earth's surface and follows the curvature of the Earth.
The propagation of high frequency wave is not possible through ground waves for long distance communication because while progressing, ground waves induce current in the ground and bend round the corner of the objects on the Earth due to which the energy of the ground waves of high frequency is almost absorbed by the surface of the Earth after travelling a small distance. Such signals are also absorbed by the obstacles (like mountains, tall buildings and trees) between the transmitter and the receiver. This loss in power of ground waves increases with the increase in frequency. Thus, ground wave communication is not suited for high frequency.
संबंधित प्रश्न
(i) Which mode of propagation is used by shortwave broadcast services having frequency range from a few MHz upto 30 MHz? Explain diagrammatically how long distance communication can be achieved by this mode.
(ii) Why is there an upper limit to frequency of waves used in this mode?
What is ground wave communication?
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