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