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प्रश्न
Line of sight propagation is also called as_________________ .
पर्याय
sky wave
ground wave
sound wave
space wave
उत्तर
space wave
APPEARS IN
संबंधित प्रश्न
Write a short note on surface wave propagation of electromagnetic waves.
(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?
State the factors which limit its range of propagation
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
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 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.
Name the three different modes of propagation of electromagnetic waves. Explain, using a proper diagram the mode of propagation used in the frequency range from a few MHz to 40 MHz.
Explain with the help of a diagram how long distance communication can be achieved by ionospheric reflection of radio waves.
What is ground wave communication? On what factors does the maximum range of propagation in this mode depend?
In sky wave mode of propagation, why is the frequency range of transmitting signals restricted to less than 30 MHz?
Answer the following question.
In the skywave mode of propagation, why is the frequency range of transmitting signals restricted to less than 30 MHz?
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?
Explain the ground wave propagation and space wave propagation of electromagnetic waves through space.
The wavelength of electromagnetic wave employed in space communication very over a range of
An antenna is
Polarization in e.m wave is caused by
Propagation constant of a transmission line is
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?
