davisnotes/lo_refraction.html

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<title>Light and Optics - Refraction - Physics 299</title>
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<h1><img src="ULPhys1.gif" align="texttop" height="50" width="189"></h1>
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<h1>Refraction</h1>
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<center><img src="celticbar.gif" height="22" width="576"> <br>
<br>
<font color="#ff0000"><i>"Technology...the knack of so arranging
the world so that we need not experience it"</i></font><br>
Max Frisch<br>
</center>
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<br>
<ul>
<li>Refraction may be defined as the <i>"bending"</i> of light
(or any EM wave) as it passes from one medium to another.
&nbsp;The bending is caused by differing speeds of the wave in
the two media.</li>
<br>
<li><b>Refractive Index</b><br>
The refractive index, n, of a medium is defined as the ratio of
the speed of light in a vacuum to the speed of light in the
medium<br>
<br>
<center><img alt="" src="lo_refraction_eqn1.gif" style="width:
219px; height: 44px;"><br>
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<br>
</li>
<li><img src="Snell.jpg" alt="Snell picture" align="left"
height="109" width="90"> <a
href="http://www-gap.dcs.st-and.ac.uk/%7Ehistory/Mathematicians/Snell.html">Snell</a>
<b> 's Law (Law of Refraction)</b>, describes exactly how much
the light is bent when passing from one medium to another.<br>
</li>
</ul>
<div align="center"><img src="lo_snellslaw.gif" alt="Snells law"
align="middle" height="101" width="306"> <br clear="all">
<div align="center"><img src="lo_refracpic.jpg" alt="Refraction
picture" align="middle" height="300" width="400"> <br>
<div align="left"><br>
<ul>
<li><b>Important points</b></li>
</ul>
<b></b>
<ul>
<ul>
<li>Light is bent towards the normal when moving into a
medium of larger refractive index.</li>
</ul>
</ul>
<ul>
<ul>
<li>Angles of incidence, reflection and refraction are all
measured with respect to the normal. <br>
</li>
</ul>
</ul>
<ul>
<ul>
<li>As a general rule the refractive index increases with
the density of &nbsp;the medium. &nbsp;For example, the
refractive index of glass (1.5) is greater than that of
water (1.33) - glass is more dense than water.</li>
</ul>
</ul>
<ul>
<ul>
<li>Light incident normally is not deflected.</li>
</ul>
</ul>
<ul>
<ul>
<li>Light rays are <i>"reversible"</i>. &nbsp;In other
words the refracted ray in the above diagram can act as
an incident ray and the incident ray will represent the
direction of the refracted ray.</li>
</ul>
</ul>
<ul>
<ul>
<li>The refractive index of a medium depends on the
wavelength of light, e.g. in glass, blue light travels
more slowly than red light.&nbsp; This phenomena is
called "dispersion".<br>
</li>
</ul>
</ul>
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<p style="font-style: italic; color: rgb(255, 0, 0);"
class="MsoNormal">What is <span style="font-size: 13.5pt;
color: rgb(0, 0, 0);">&#960;</span>?<br>
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0);">&#960;</span><span style="color: rgb(0, 0, 0);"> </span>is
the ratio of the circumference of a circle to its diameter."<br>
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is about 22/7."<br>
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0);">&#960;</span> is 3.14159 plus or minus 0.000005."<br>
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rgb(0, 0, 0);">&#960;</span> is 3.141592653589 in double
precision."<br>
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style="font-size: 13.5pt; color: rgb(0, 0, 0);">Pie</span> is
a healthy and delicious dessert!"</p>
<br>
<img src="celticbar.gif" height="22" width="576"><br>
&nbsp;
<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>
&nbsp; </p>
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