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प्रश्न
Describe briefly, by drawing suitable diagram, the sky wave ?
उत्तर
In the frequency range from a few MHz up to 30-40 MHz, long distance communication can be achieved by ionospheric reflection of radio waves back towards the earth. This mode of propagation is called sky wave propagation. The ionosphere consists of large number of ions or charged particles due to ionisation in the presence of ultraviolet rays. The degree of ionisation varies with height. At a certain height, there occurs a peak of ionisation density which acts as a reflector of certain range of frequencies. This phenomenon is shown in the figure below:
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