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Mention three different modes of propaga...

Mention three different modes of propagation used in communications system. Explain with the help of a diagram how long distance communication can be achieved by ionospheric reflection of radio waves?

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See Q.21, Set-III, Delhi Board, 2010.
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Distinguish between Sky wave and Space wave modes of propagation in a communication system.

Which mode of propagation is used by short wave broadcast services having frequency range from a few MHz upto 30 MHz ? Explain diagrammatically how long distance communication can be achieved by this mode . Why is there an upper limit to frequency of waves used in this mode ?

With the help of circuit diagram, explain how a meter bridge can be used to find unknown resistance of a given wire?

A : Long distance radio broadcasts use short-wave bands. R : Ionosphere reflectes waves in these bands.

Two waves A and B of frequencies 2MHz and 3 MHz, respectively are beamed in the same direction for communication via sky wave. Which one of these is likely to travel longer distance in the ionosphere before suffering total internal reflection?

XII BOARDS PREVIOUS YEAR-XII BOARDS-PHYSICS (Theory) [SET - I]
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