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• Dr. S. Cruz-Pol, INEL 4152-Electromagnetics Electrical Engineering, UPRM
• ### Emw

1. 1. PROPAGATION OF ELECTRO MAGNETIC WAVES PRESENTED BY Dr.V.SUKANYA
2. 2. DEFINITION OF E.M.WAVES: The wave of the electric field and the wave of the magnetic field are propagated perpendicularly to the direction of propagation and to each other. At extremely low frequencies, the electric field and the magnetic field are specified separately. At higher frequencies, electric and magnetic fields are not separable, and are named "electromagnetic waves" or "electromagnetic fields".
3. 3. Nature of Electromagnetic WavesThey are Transverse waves without a medium. (They can travel through empty space)They travel as vibrations in electrical and magnetic fields.Have some magnetic and some electrical properties to them.Speed of electromagnetic waves = 300,000,000 meters/second (Takes light 8 minutes to move from the sun to earth {150 million miles} at this speed.)
4. 4. Ground-Wave PropagationAt frequencies up to about 2 MHz, the most important method of propagation is by ground waves which are vertically polarized. They follow the curvature of the earth to propagate far beyond the horizon. Relatively high power is required. Direction of wave travel Increasing Tilt Earth
5. 5. SPACE WAVE PROPAGATIONThe EM wave that propagates from the transmitter to the receiver in the earth’s troposphere is called “Space Wave”.Troposphere is the region of the atmosphere with in 15km above the surface of the earth.The Maximun line of sight distance between two antenns depends on the height of each antenna.
6. 6. SKYWAVE PROPAGATIONSky wave propagation is also called Ionospheric wave propagation. E.M waves directed upward at some angle from the earth’s Surface are called Skywaves.Sky wave propagation is usefull in the frequency range of 2 to 30 MHz and for long distance communicationIonosphere is the upper portion of the atmosphere between 50km and 350km above the earth,which is ionoised by absorbing large quantities of radiation energy from the Sun.The Major ionisation is from α,β and γ radiation from the Sun and cosmic rays and meter
7. 7. ReflectionRefractionDiffractionPolarizationScattering
8. 8. Reflection:Reflection is when waves, whether physical or electromagnetic, bounce from asurface back toward the source. A mirror reflects the image of the observer.
9. 9. Polarization:The polarization of an electromagnetic wave indicates the planein which it is vibrating. As electromagnetic waves consist of anelectric and a magnetic field vibrating at right angles to eachother it is necessary to adopt a convention to determine thepolarization of the signal. For this purpose the plane of theelectric field is used.
10. 10. Refraction:Refraction is the bending of light as it passes between materials of different optical density Refraction of a material is the ratio of the speed of light in vacuum to the speed of light in that material: n=
11. 11. Diffraction:When a travelling water wave hits an obstacle, the wave fronts spreads out roundthe edge and becomes curved. This phenomenon refers to diffraction
12. 12. Scattering:The change in direction of a particle or photon because of a collision with anotherparticle or a system.