149 lines
6.8 KiB
HTML
149 lines
6.8 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 - Polarisation - 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);" alink="#ff0000" link="#0000ee" vlink="#551a8b">
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<center>
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<h1><img src="ULPhys1.gif" align="texttop" height="50" width="189">
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</h1>
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</center>
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<center>
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<h1>Polarisation</h1>
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</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>"</i></font><font color="#ff0000"><i>
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<meta http-equiv="content-type" content="text/html;
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charset=windows-1252">
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</i></font>
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<div style="overflow: hidden; color: rgb(0, 0, 0);
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background-color: rgb(255, 255, 255); text-align: left;
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text-decoration: none; border: medium none; position: absolute;
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left: -99999px;" id="r1PostCPBlock">A physicist is just an
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atom's way of looking at itself.<br>
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<span>Read more at <a style="color: #003399;"
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href="http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99">http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99</a></span></div>
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<font color="#ff0000"><i>
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<meta http-equiv="content-type" content="text/html;
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charset=windows-1252">
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</i></font>
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<div style="overflow: hidden; color: rgb(0, 0, 0);
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background-color: rgb(255, 255, 255); text-align: left;
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text-decoration: none; border: medium none; position: absolute;
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left: -99999px;" id="r1PostCPBlock">A physicist is just an
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atom's way of looking at itself.<br>
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<span>Read more at <a style="color: #003399;"
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href="http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99">http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99</a></span></div>
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<font color="#ff0000"><i>
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<meta http-equiv="content-type" content="text/html;
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charset=windows-1252">
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</i></font>
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<div style="overflow: hidden; color: rgb(0, 0, 0);
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background-color: rgb(255, 255, 255); text-align: left;
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text-decoration: none; border: medium none; position: absolute;
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left: -99999px;" id="r1PostCPBlock">A physicist is just an
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atom's way of looking at itself.<br>
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<span>Read more at <a style="color: #003399;"
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href="http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99">http://www.brainyquote.com/quotes/quotes/n/nielsbohr382329.html#urRTQl9BfaJk3yj3.99</a></span></div>
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<font color="#ff0000"><i>A physicist is just an atom's way of
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looking at itself" </i></font><br>
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Niels Bohr<br>
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</center>
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<img src="netbar.gif" align="middle" height="40" width="100%"> <br>
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<br>
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<ul>
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<li>We have seen that electromagnetic waves may be described by
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transverse waves of <b>E</b> and <b>B</b> (at right angles to
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each other). However, there is nothing special about any
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particular direction for the <b>E</b> or <b>B</b> vectors to
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oscillate. In fact an <b>unpolarised</b> wave contains
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waves with <b>E</b> vectors in all possible directions (for
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each <b>E</b> wave there is a <b>B</b> wave at right
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angles). If the wave propagates in the z direction this
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wave has <b>E</b> components in all possible directions.</li>
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</ul>
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<ul>
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<li>In a polarised wave the <b>E</b> vector oscillates in a
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specific direction - the direction of polarisation.</li>
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</ul>
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<div align="left">
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<ul>
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<li>Polarised light does not appear any different to unpolarised
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light to our eyes. The difference only becomes apparent
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when observing through transparent polarising material,</li>
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</ul>
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<div align="center"><img alt="polarisation fig1"
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src="lo_polarisation1.jpg" height="218" width="500">
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<img alt="polarisation fig2" src="lo_polarisation2.gif"
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height="190" width="423"><br>
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<br>
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<div align="left">
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<ul>
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<li>The intensity of initially unpolarised light which
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passes through two polarisers is given by <a
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href="http://micro.magnet.fsu.edu/optics/timeline/people/malus.html"><img
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alt="malus" src="lo_malus.jpg" align="middle"
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border="0" height="128" width="94"></a><a
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href="http://www.physicshandbook.com/laws/maluslaw.htm">Malus'
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Law,</a></li>
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</ul>
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<div align="center"><img alt="polarisation eqn1"
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src="lo_polarisation_eqn1.jpg" height="56" width="141"><br>
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<blockquote>
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<div align="left">where I<sub>0</sub> is the incident
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intensity and θ is the angle between the directions of
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the two polarisers. Note that for "cross
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polarisers" there is no transmitted wave.<br>
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</div>
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</blockquote>
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<div align="left">
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<ul>
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<li><img alt="hot" src="hot.gif" align="middle"
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height="43" width="79"> Analog TV and radio
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signals are transmitted as polarised waves. When
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rotating the direction of an antenna you are
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effectively rotating the second polariser, thus
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varying the angle θ. Maximum and minimum signal
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reception will be obtained with orientations of the
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antenna at ninety degrees to each other.<br>
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</li>
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</ul>
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</div>
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<blockquote>
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<div align="left"> </div>
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</blockquote>
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</div>
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</div>
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</div>
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</div>
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<br>
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<img src="netbar.gif" height="40" width="100%"><br>
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<center>"<span style="font-style: italic; color: rgb(255, 0, 0);">Alimony
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is like buying hay for a dead horse"</span><br>
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Groucho Marx<br>
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<br>
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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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