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<p>[QUOTE=&quot;Insider, post: 8292613, member: 24314&quot;]ToughCOINS, posted:</p><p><br /></p><p>Surface area perpendicular to the light source determines how concentrated and bright the reflected light is.</p><p><i><span style="color: #660033">So I guess you voted for 3 o&#039;clock?</span></i></p><p><br /></p><p>1.&nbsp; <i>Light directed along the length of the scratch will reflect in the direction of the scratch.&nbsp; One might expect the light reflected by the full length of the scratch to be very bright</i>, but it will be diffuse because of the varying angle of incidence (think varying focal distance and / or depth of field for a lens) along the length of the scratch.</p><p><br /></p><p><i><span style="color: #660033">On the right track. Members my wish to take a circulated brown cent and put a straight, light, scratch on it and do an experiment to see if this is true.&nbsp; </span></i></p><p><br /></p><p>2.&nbsp; Lighting from 6:00 or 12:00 would reflect out the far end of the scratch, and not perpendicular to it, as would lighting from 3:00 or 9:00.</p><p><br /></p><p><i><span style="color: #660033">On the right track.</span></i></p><p><br /></p><p>3.&nbsp; The scratch is not straight.&nbsp; Curved as it is, I&#039;d expect the reflected light from 3:00 to concentrate more, as if reflected by a parabolic mirror, while light directed at the scratch from 9:00 should disperse somewhat, and be less bright.&quot;</p><p><br /></p><p><span style="color: #660033"><i>This is out-of-the-box thinking that I never considered.&nbsp; It would make a nice project for an optical lab to confirm this.</i></span></p><p><span style="color: #660033"><br /></span></p><p><span style="color: #660033"></span>[/QUOTE]</p><p><br /></p>

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