131 lines
5.6 KiB
HTML
131 lines
5.6 KiB
HTML
<!DOCTYPE html PUBLIC "-//w3c//dtd html 4.0 transitional//en">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html;
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charset=windows-1252">
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<meta name="GENERATOR" content="Mozilla/4.7 [en] (X11; U; OSF1 V4.0
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alpha) [Netscape]">
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<meta name="Author" content="C. L. Davis">
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<title>Light and Optics - Electromagnetic Waves - Physics 299</title>
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</head>
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<body style="color: rgb(0, 0, 0); background-color: rgb(255, 255,
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255);" link="#0000ee" vlink="#551a8b" alink="#ff0000">
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<center><img src="ULPhys1.gif" height="50" width="189"
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align="texttop"> </center>
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<h1>
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<center>Electromagnetic Waves</center>
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</h1>
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<center></center>
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<center><img src="celticbar.gif" height="22" width="576"> <br>
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<br>
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<font color="#ff0000"><i>"Basic research is what I am doing when I
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don't know what I am doing"</i></font><br>
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Wernher von Braun<br>
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</center>
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<img src="netbar.gif" height="40" width="100%" align="middle"> <br>
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<br>
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<ul>
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<li> At the end of the nineteenth century <a
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href="http://www.phy.hr/%7Edpaar/fizicari/xmaxwell.html">
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James Clerk Maxwell</a> was responsible for bringing together
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the work of Coulomb, Ampere, Faraday and others, to provide an
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elegant theoretical description of electricity and magnetism.
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Classical electromagnetism was described by four <i>"simple"</i>
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equations known as <a href="lo_maxeqn.gif"> Maxwell's equations</a>
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. These equations provided the <i>"explanation"</i> for
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electromagnetic waves.<br>
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<br>
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</li>
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<li>An electromagnetic wave is a transverse wave comprised of
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oscillating Electric and Magnetic fields. Mathematically
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the analysis of EM waves is rather complex. A plane
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polarised electromagnetic wave traveling from left to right can
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be represented as indicated below.</li>
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<div align="center"><img src="lo_e_mag.gif" alt="emwave"
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height="268" width="506" align="middle"> <br>
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<div align="left"> The "traveling nature of the wave is
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represented thus,<img src="lo_emwave.gif" alt="emwave2"
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height="75" width="100" align="middle"> where <b>E </b>represents
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the electric field and <b> H</b> the magnetic field.<br>
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<br>
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</div>
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</div>
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<li>Visible light is a very small part of the electromagnetic
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spectrum. The full EM spectrum extends continuously from
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the very low frequency <b>E</b> and <b>B </b>oscillations of
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radio waves through microwaves, infra-red, visible light,
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ultra-violet, X-rays to very high frequency gamma rays.<br>
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<br>
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<div align="center"><img src="lo_EMSpec.gif" alt="EM spectrum"
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height="339" width="687" align="middle"> </div>
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</li>
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<br>
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<li> The speed of electromagnetic waves (of all frequencies and
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wavelengths) in a vacuum is equal to the speed of light, c = 3 x
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10<sup>8 </sup> m/s. Speed, frequency (f) and
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wavelength (<img alt="" src="lo_emwaves_eqn2.gif" style="width:
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13px; height: 17px;" align="middle">) are related by the usual
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relationship<br>
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<br>
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<div align="center"><img alt="loemwaveseqn2"
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src="lo_emwaves_eqn2.jpg" height="55" width="120"></div>
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</li>
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<li> Using Maxwell's equations it can be shown that the speed
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of light is given by <br>
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</li>
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</ul>
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<div align="center"><img alt="loemwaveseqn1"
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src="lo_emwaves_eqn1.jpg" height="90" width="134"></div>
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<ul>
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<br>
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<br>
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<li> Using Maxwell's decription of electromagnetic waves it is
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possible to explain many of the properties of the interactions
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of visible light with matter. The details of such
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explanations are technically quite difficult and are
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typically covered in senior level Physics courses. In the
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following discussion we will investigate some of the
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consequences of these properites, for example, the law of
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reflection, law of refraction (Snell's law), total internal
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reflection, dispersion, interference and diffraction. </li>
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</ul>
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<ul>
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<li>The electromagnetic spectrum NASA <a
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href="https://www.youtube.com/watch?v=cfXzwh3KadE">video</a>.</li>
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</ul>
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<ul>
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<li>Maxwell brief biography <a
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href="https://www.youtube.com/watch?v=LjY1x5CDvD4&list=PL5CvBU3RbkTfWpegYEnCOzbG-JTdu8Hpf">video.</a><br>
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</li>
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</ul>
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<ul>
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<li>Maxwell's equations and electromagnetic waves <a
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href="http://www.youtube.com/watch?v=VdoL8IOwJw0">video.</a><br>
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</li>
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</ul>
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<ul>
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</ul>
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<img src="netbar.gif" height="40" width="100%"><br>
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<center>
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<p class="MsoNormal"><span style="font-style: italic; color:
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rgb(255, 0, 0);">"I've heard that the government wants to put
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a tax on the mathematically ignorant. Funny, I thought that's
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what the lottery was!"</span><br>
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Gallagher<span style="color: blue;"><o:p></o:p></span></p>
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<img src="celticbar.gif" height="22" width="576"> <br>
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<p><i>Dr. C. L. Davis</i><br>
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<i>Physics Department</i><br>
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<i>University of Louisville</i><br>
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<i>email</i>: <a href="mailto:c.l.davis@louisville.edu">c.l.davis@louisville.edu</a>
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<br>
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</p>
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<p><img src="header-index.gif" height="51" width="92"> </p>
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</center>
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<p><br>
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</p>
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</body>
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</html>
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