davisnotes/lo_reflection.html

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<title>Light and Optics - Reflection - Physics 299</title>
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<h1><img src="ULPhys1.gif" align="texttop" height="50" width="189"> </h1>
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<center>
<h1>Reflection</h1>
</center>
<center><img src="celticbar.gif" height="22" width="576"> <br>
<br>
<font color="#ff0000"><i>"We believe a scientist because he can
substantiate his remarks, not because he is eloquent and forcible in
his enunciation. &nbsp;In
fact we distrust him when he seems to be influencing us by his manner"</i></font><br>
I. A Richards<br>
</center>
<img src="netbar.gif" align="middle" height="40" width="100%"> <br>
<div align="center"><img src="lo_reflpic.jpg" alt="reflection picture"
align="middle" height="314" width="398"> <br>
<i><a
href="http://www.3d-dali.com/Artist-Biographies/Edouard_Manet.html">Edouard
Manet</a> - A bar at the Folies_Bergere</i><br>
<small>Spot the deliberate(?) mistakes</small><br>
</div>
<ul>
<li>A general description of the reflection of electromagnetic waves
is obtained by considering the wave nature of the radiation.
&nbsp;However, when the wavelength of the radiation is small compared
to any apertures or obstacles nearby we may treat the wave as a stream
of <i>"particles"</i> traveling in a straight line. &nbsp;This is the
situation when considering the formation of images by visible light in
mirrors and lenses. In this case the straight lines
in which the visible light waves travel are known as <b><i> light rays</i></b>
. &nbsp;The study of the behaviour of&nbsp; light under these conditons
is known as Geometric Optics.</li>
<br>
<li>Light rays undergo one of &nbsp;two types of &nbsp;reflection -
diffuse or specular.<br>
<br>
<ul>
<li>Diffuse reflection is more common for almost all objects.
&nbsp;The reflected light is emitted in all directions due to
irregularities on the surface of the material.</li>
<li>Specular reflection occurs if the irregularities of the
surface are small compared to the wavelength of the light. &nbsp;In
this case reflection occurs at a single angle, for example from the
surface of a plane mirror or water.</li>
</ul>
<div align="center"><img src="lo_speculardiffuse.jpg"
alt="specular /diffuse refelction" align="middle" height="194"
width="465"> <br>
</div>
We will consider only specular reflection in
this course<br>
</li>
<br>
<li><u><b>The law of reflection</b>.</u>(which can be derived from
Maxwell's equations)<br>
<br>
<div align="center"> Angle of incidence = angle of reflection </div>
<br>
Angles are measured with respect to the normal to the surface.</li>
<div align="center"><img src="lo_refl1.gif" alt="reflection1"
align="middle" height="86" width="161"> &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;<img src="lo_anim_refl2.gif" alt="reflection2" align="middle"
height="308" width="223"> <br>
</div>
<li><u><b>Ray Tracing and Image Formation in a plane mirror</b></u><br>
<br>
Light rays are reflected from a plane mirror according to
the law of reflection. An image is formed on the "other" side of the
mirror, where the reflected rays <i>appear</i> to originate.</li>
</ul>
<div align="center"><img src="lo_refl4.gif"
alt="reflection from plane mirror" align="middle" height="299"
width="324"> </div>
<ul>
<br>
<li> Images formed in plane mirrors have the
following properties,<br>
<br>
<ul>
<li>Located the same distance behind the mirror as the object is
in front of the mirror.</li>
<li>Same size as the object.</li>
<li>Right and left inversion<br>
</li>
<li>Upright</li>
<li><b>Virtual</b></li>
</ul>
<br>
An image is <b>virtual</b> if light rays do not physically pass
through it. &nbsp;Real images are formed if light rays actually pass
through the image. </li>
</ul>
<img src="netbar.gif" height="40" width="100%">
<center><br>
<span style="font-style: italic; color: rgb(255, 0, 0);">"The
tides are a fight between the Earth and Moon. All water tends
towards the moon, because there is no water in the moon, and nature
abhors a
vacuum. I forget where the sun joins in this fight."</span><br>
Middle School Science Test Answer<br>
<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>
<p><img src="header-index.gif" height="51" width="92"> </p>
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