Lect 3.1 - Department of Electrical and Computer...

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Department of Electrical and Computer Engineering ECSE 352 Electromagnetic Waves and Optics Module 3: Reflection and dispersion of waves 3.1 Wave reflection at normal incidence References: Section 13.1 AGK@2005 3.1-1 Dispersion and reflection in nature Overview When we studied transmission lines we saw that many important effects arise when waves move from one medium to another. Similar effects arise for electromagnetic waves in space, d at hat e ill udy is ction f e ourse verywhere at ave and that is what we will study in this section of the course. Everywhere that a wave experiences a change in the characteristics of the medium that it is traveling in, we need to consider whether any power will be reflected. The phenomenon of reflection is something we are all very familiar with - particularly at optical frequencies. However reflection is also important at radio frequencies - both as desired effect, such as when we want to make a flecting dio ntenna d s wanted roblem ch hen dio gnals flect f reflecting radio antenna, and as an unwanted problem such as when radio signals reflect off the ground and cause multi-path interference. Anyone who has ever seen a fairground mirror knows that when waves reflect off curved surfaces, the wavefront can be distorted in all sorts of ways. Here we will consider just planar reflecting surfaces, and plane waves, and so the calculations will be simple. We will start by introducing the concept of boundary conditions for EM waves and see how an interface can be classified as a set of boundary conditions. In this session we will concentrate on waves incident onto conducting boundaries - e.g. light incident onto a metal mirror. When the boundary is with a perfect conductor, all the power will be reflected, with y p p no loss. Since as much power is now traveling backwards as was going forwards, this means that there is no net transfer of power through the boundary. As was the case in transmission lines, the wave in the region on front of the boundary is described as a standing wave . ECSE 352 3.1-3 Module 3: Reflection and dispersion Module 1: Transmission Lines Module 2: The Uniform Plane Wave Module 3: Reflection and dispersion of waves 1. Plane wave reflection at normal incidence 2. Standing wave ratio for plane waves ave reflection from multiple interfaces 3. Wave reflection from multiple interfaces 4. Wave propagation in arbitrary directions 5. Plane wave reflection at oblique incidence 6. Special reflection cases
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Lect 3.1 - Department of Electrical and Computer...

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