93 lines
3.7 KiB
HTML
93 lines
3.7 KiB
HTML
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<!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"
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content="text/html; charset=ISO-8859-1">
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<meta name="GENERATOR"
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content="Mozilla/4.7 [en] (X11; U; OSF1 V4.0 alpha) [Netscape]">
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<meta name="Author" content="C. L. Davis">
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<title>Light and Optics - Dispersion - Physics 299</title>
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</head>
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<body style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"
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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"> </h1>
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</center>
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<center>
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<h1>Dispersion</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>"To err is human but to really foul things up
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requires a computer"</i></font><br>
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Anonymous<br>
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<small><small>(Farmers Almanac 1978)</small></small><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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<div align="center"><a href="http://www.pinkfloyd.com/"><img
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src="dsotm1.gif" alt="Dark Side"
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style="border: 0px solid ; width: 143px; height: 112px;" align="middle">
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</a> </div>
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<ul>
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<li>Without explicitly making the statement we have assumed that the
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refractive index of a medium is independent of the frequency of the
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light transmitted. That is we have assumed for example that red
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light and blue light have the same speed when passing through glass (or
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any other medium). This is not exactly true, refractive index is
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frequency dependent such that for glass, n<sub>blue</sub> > n<sub>red</sub>
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(blue light is bent more than red light when passing from air to glass)
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and the speed of blue light in glass is slightly smaller than the speed
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of red light.</li>
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<br>
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<li>This fact may be demonstrated by the production of a spectrum of
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colours when <i>white</i> light is incident on a glass prism. [White
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light is comprised of all the wavelengths of visible light] Each
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constituent of the white light has a slightly different refractive
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index and is deflected (according to Snell's law) through a slightly
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different angle. <br>
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<br>
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<div align="center"><img src="lo_anim_prism_anim.gif" alt="Prism"
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align="middle" height="175" width="400"> </div>
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</li>
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<br>
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<li>This phenomenon is known as <b><i>DISPERSION</i></b>.
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White light is <b><i>dispersed</i></b> into its constituent
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colours.</li>
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<br>
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<li>A rainbow is created by a combination of dispersion and total
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internal reflection within water droplets in the atmosphere.<br>
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<div align="center"><img src="lo_rainbowgirltwodrops.jpg"
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alt="Rainbow" align="middle" height="291" width="444"> </div>
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</li>
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<br>
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<li>An object appears a particular colour under white light
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illumination because it <b><i>reflects</i></b> that colour strongly.<br>
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<div align="center"><img src="lo_colour.gif" alt="Colours"
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align="middle" height="120" width="183"> <br>
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</div>
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For example a red object <i>reflects</i> most of the red wavelength
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incident and <i>absorbs</i> most of the other wavelengths. If
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such an object is illuminated with blue light it will appear black,
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the blue light is absorbed, but there is no red to be reflected. </li>
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</ul>
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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);">There
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is no Dark Side of the Moon really. Matter of fact it's all dark"</span><br>
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Pink Floyd<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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