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प्रश्न
Mention three different modes of propagation used in communication system.
उत्तर
Three modes of propagation of electromagnetic waves,
(a) Ground waves,
(b) Sky waves,
(c) Space waves.
Sky wave propagation is used for long distance communication by ionospheric reflection of radio waves.
संबंधित प्रश्न
Line of sight propagation is also called as_________________ .
The outermost layer of the earth’s atmosphere is _______.
(A) stratosphere
(B) mesospher
(C) troposphere
(D) ionosphere
Is it necessary for a transmitting antenna to be at the same height as that of the receiving antenna for line-of-sight communication? A TV transmitting antenna is 81m tall. How much service area can it cover if the receiving antenna is at the ground level?
Explain with the help of a diagram how long distance communication can be achieved by ionospheric reflection of radio waves.
Name the three different modes of propagation in a communication system. State briefly why do the electromagnetic waves with a frequency range from a few MHz up to 30 MHz can reflect back to the earth. What happens when the frequency range exceeds this limit?
What do you mean by skip distance?
The Q of a resonant transmission line is
What is the value of frequency at which an e.m wave must be propagated for the D-region of atmosphere to have a refractive index of 0.49? Electron density for D-region is 109 m-3:
Three waves A, B and C of frequencies 1600 kHz, 5 MHz and 60 MHz, respectively are to be transmitted from one place to another. Which of the following is the most appropriate mode of communication ______.
(i) The intensity of a light pulse travelling along a communication channel decreases exponentially with distance x according to the relation I = Ioe–αx, where Io is the intensity at x = 0 and α is the attenuation constant. Show that the intensity reduces by 75 per cent after a distance of `((In 4)/α)`
(ii) Attenuation of a signal can be expressed in decibel (dB) according to the relation dB = `10 log_10 (I/I_0)`. What is the attenuation in dB/km for an optical fibre in which the intensity falls by 50 per cent over a distance of 50 km?
