Importance Of POC Unit In Physics-Kumar Physics Classes
The word space communication refers to sending receiving and processing of information through space.
There are three types of space communication.
This mode of propagation can exist when the transmitting and receiving antenna are close to the surface of the earth. For radiating high-efficiency signals, the size of the antenna should be of the order of l/4. l = wavelength of the signal.
The field component of such a launched wave soon becomes vertically polarized as it glides over the surface of the planet.
The electrical fields intensity due to the wave induce large charges on the earth’s surface. The ground wave is weakened as a result of energy absorbed by the earth during its propagation. These losses make ground waves unsuitable for very long-range communication.
Ground wave propagation should be sustained only at low frequencies
(~ 500 kHz to 1500 kHz) or for radio broadcast at long wavelengths.
A transmitted wave going up is reflected back by the ionosphere which forms an ionised layer of electrons and ions around the earth. The ionosphere (including
mesosphere and part of the stratosphere) extends from about 65 km to 400 km above the earth’s surface. Constituent gases are ionised in it by solar radiation. Throughout the ionosphere, there are several layers in which the ionisation density either reaches a maximum or remains roughly constant. These regions are designated as D(65-75 km), E(100 km) and F(130 km-400 km) in order of approximate heights above earth’s surface. During daytime, the F layer splits into separate layers called F1 (170-190 km over earth’s surface) and F2 (250- 400 km over earth’s surface). During night F1 layer usually disappears.
Region of high conductivity is confined to a relatively thin layer at the lower edge of E-region and to the upper part of D-region. Therefore high frequencies are attenuated when they penetrate this region. D and E layer disappears during night and low and medium frequency communication also becomes possible. Ionisation density increases as we go up from D layer to F layer and then decreases, due to which their respective refractive indices vary. Therefore the transmitted wave is reflected back in a way similar to the phenomenon of total internal refraction.
This mode is also known as line of sight communication. To send signals at far away stations, either repeater transmitting stations are necessary or height of the transmitter is increased by locating it in a satellite. If hT is the height of transmitting antenna and dT is the distance to the horizon from it, then dT = Root 2RhT , where R is the radius of the earth. dT is called radio horizon of transmitting antenna.
The maximum line-of-sight distance dM between the two antennas having heights hT and hR above the earth is given by
dM = Root 2RhT + Root 2RhR
[scribd id=377972610 key=key-rejaQt7JqlwOylfOQ8ZF mode=scroll]
Still You Feel any problem in physics contact kumar sir Directly- for better result in Cbse
Physics Exam,NEET Physics Exam,IIT Physics Exam
CLASSES FOR CBSE XI,XII WITH
for any level
AND CLEAR ALL CONCEPTS TO ACHIEVE 100% SUCCESS IN XI,XII,NEET,IIT
KUMAR PHYSICS CLASSES
E 281 BASEMENT M BLOCK MAIN ROAD GREATER KAILASH 2 NEW DELHI
Do Hard Work In Physics And Get Success In Physics Exam ,Do Atleast 100 Physics Mcq’s a Day
Physics Tutor In Alaknanda,Physics Tutor In saket,physics tutor in green park,physics tutor in hauz khas,physics tutor in khel gaon ,[scribd id=377972610 key=key-rejaQt7JqlwOylfOQ8ZF mode=scroll] tutor in gk 1,physics tutor in jasola vihar,physics tutor in sarita vihar,physics tutor in nfc,physics tutor in ashram,physics tutor in noida,physics tutor in gurgaon,physics tutor in vasant vihar,physics tutor in r k puram dps,physics tutor in safdarjung enclave,physics tutor in nehru place,physics tutor in mandakini,physics tutor in vasant vihar all blocks,physics tutor in sant nagar,physics tutor in amar colony,physics tutor in lajpat nagar,physics tutor in jangpura extension,physics tutor in malviya nagar