new ccna 200-301 exam

new ccna 200-301 exam.Scattering has a greater effect on signals with shorter wavelengths, and the effect depends on the frequency. The result of scattering is a weaker signal. 6. Understanding RefractionRefraction ( refi*acticm) is the change in the direction of propagation, or bending, of a waveform passing through matter of different density.28 Chapter 3 Principles of Wireless LAN RFbend. This behavior causes part of the signal to be reflected out and part of the signal to be bent through the object. To better understand this concept, Figure 3-7 demonstrates the effect of refraction. A waveform is passing through a glass of water. Note that because of the reflective nature of the glass, a portion of the light is reflected while another portion still manages to pass through.After passing through the glass, the angle of propagation of the waveform changes.Note: You can see examples of the effects of subtle refraction at http://www.phy.hk/wiki/englishhtm/RefractionByPrism.htm Java.Refraction usually has a greater effect on outdoor signals, with dryness moving the refraction away from the ground (e.g., dust particles) and moisture moving the refraction toward the ground.7. Understanding Sight DistanceAs an object moves in the direction of the receiver, it may have to deal with various obstacles that it encounters directly in its path. These obstacles in the path can cause a variety of the problems just discussed: absorption, reflection, refraction, and scattering. When a wireless signal travels a long distance, the signal near the midpoint becomes wider and the signal closer to the receiving end becomes narrower. Figure 3-8 shows two directional antennas that are sending a signal between two points. This seemingly straight-line range (straightshot) is called the line-of-sight (LOS, LineOfSight) 0 Although there are no obvious obstacles in this path, the earth itself becomes an obstacle because of the great distance. This means that the curvature of the earth, mountains, trees, and other environmental obstacles can, in fact, interfere with the signal.Figure 3-8 Directional antenna and line-of-sightEven if you see the other endpoint in a straight line, it is important to remember that the signal does not travel in a straight line. The signal actually varies