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<a accesskey="3" href="page.php?w=optical_depth&amp;p=2">3.Next</a>
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<p>In <a href="page.php?w=physics">physics</a>, <b>optical depth</b> or <b>optical thickness</b> is the <a href="page.php?w=natural_logarithm">natural logarithm</a> of the ratio of incident to transmitted <a href="page.php?w=radiant_power">radiant power</a> through a material.Thus, the larger the optical depth, the smaller the amount of transmitted radiant power through the material. <b>Spectral optical depth</b> or <b>spectral optical thickness</b> is the natural logarithm of the ratio of incident to transmitted <a href="page.php?w=Radiant_power">spectral radiant power</a></p><p>
<a accesskey="3" href="page.php?w=optical_depth&amp;p=2">3.Next</a>
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