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प्रश्न
What is space wave propagation?
उत्तर
Space wave propagation: When the radio waves from the transmitting antenna propagate along the space surrounding the earth to reach the receiving antenna, either
directly or after reflection from the ground or in the troposphere, the wave propagation is called Space wave propagation.
संबंधित प्रश्न
Write a short note on surface wave propagation of electromagnetic waves.
Line of sight propagation is also called as_________________ .
(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?
The outermost layer of the earth’s atmosphere is _______.
(A) stratosphere
(B) mesospher
(C) troposphere
(D) ionosphere
What is space wave propagation?
State the factors which limit its range of propagation
Derive an expression for the maximum line of sight distance between two antennas for space wave propagation.
What is ground wave communication?
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?
In which directions do the electric and magnetic field vectors oscillate in an electromagnetic wave propagating along the x-axis?
The reflected waves from an ionosphere are _____.
(a) ground waves
(b) sky waves
(c) space waves
(d) very high-frequency waves
Four nuclei of an element undergo fusion to form a heavier nucleus, with release of energy. Which of the two – the parent or the daughter nucleus – would have higher binding energy per nucleon?
Explain why this mode cannot be used for long distance communication using high frequencies.
Is it necessary for a transmitting antenna to be at the same height as that of receiving antenna for LOS communication ?
Describe briefly, by drawing suitable diagram, the sky wave ?
Describe briefly, by drawing suitable diagram, the space wave modes of propagation. Mention the frequency range of the waves in these modes of propagation ?
An em wave is travelling in a medium with a velocity `vecv =vhati` Draw a sketch showing the propagation of the em wave, indicating the direction of the oscillating electric and magnetic fields.
Mention three different modes of propagation used in communication system.
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?
Light from a sodium lamp (S) passes through two polaroid sheets P1 and P2 as shown in fig. What will be the effect on the intensity of the light transmitted (i) by P1 and (ii) by P2 on the rotating polaroid P1 about the direction of propagation of light? Justify your answer in both cases.
What do you mean by skip distance?
The length of half wave dipole at 30MH2 is
The Q of a resonant transmission line is
In He-Ne loser the most favourable ratio of Helium toNe on for satisfactory laser action is
Propagation constant of a 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 ______.
A TV transmission tower has a height of 240 m. Signals broadcast from this tower will be received by LOS communication at a distance of (assume the radius of earth to be 6.4 × 106 m)
- 100 km
- 24 km
- 55 km
- 50 km
The maximum frequency for reflection of sky waves from a certain layer of the ionosphere is found to be fmax = 9(Nmax)1/2, where Nmax is the maximum electron density at that layer of the ionosphere. On a certain day, it is observed that signals of frequencies higher than 5 MHz are not received by reflection from the F1 layer of the ionosphere while signals of frequencies higher than 8 MHz are not received by reflection from the F2 layer of the ionosphere. Estimate the maximum electron densities of the F1 and F2 layers on that day.
(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?
A 50 MHz sky wave takes 4.04 ms to reach a receiver via re-transmission from a satellite 600 km above earth’s surface. Assuming re-transmission time by satellite negligible, find the distance between source and receiver. If communication between the two was to be done by Line of Sight (LOS) method, what should size and placement of receiving and transmitting antenna be?
