Refractive index: Difference between revisions

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Complex refractive index: delete content that does not verify. The MIT course notes say nothing about mass attenuation.
Complex refractive index: correct content per ref
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|archive-url = https://web.archive.org/web/20150724051216/http://web.mit.edu/course/6/6.732/www/6.732-pt2.pdf
|archive-date = 2015-07-24
}}</ref>{{rp|36}} or ''[[absorption coefficient]]'' and indicates the amount of attenuation when the electromagnetic wave propagates through the material.<ref name="Hecht"/>{{rp|p=128}} It is related to the ''[[absorption coefficient]]'', <math>\alpha_\text{abs}</math>, through:<ref name=DresselhausMITCourse/>{{rp|41}}
<math display="block">\alpha_\text{abs}(\omega) = \frac{2\omega\kappa(\omega)}{c}</math>
These values depend upon the frequency of the light used in the measurement.
 
That {{mvar|κ}} corresponds to absorption can be seen by inserting this refractive index into the expression for [[electric field]] of a [[plane wave|plane]] electromagnetic wave traveling in the {{mvar|x}}-direction. This can be done by relating the complex [[wave number]] {{mvar|{{uu|k}}}} to the complex refractive index {{mvar|{{uu|n}}}} through {{math|{{uu|''k''}} {{=}} 2π{{uu|''n''}}/''λ''{{sub|0}}}}, with {{math|''λ''{{sub|0}}}} being the vacuum wavelength; this can be inserted into the plane wave expression for a wave travelling in the {{mvar|x}}-direction as: