The second layers are generally one quarter wavelength optical thickness at a particular tuned wavelength, whereas the first layers are generally {HEAD ~ a plurality} of {TAIL ~ quarter wavelength optical thicknesses} 
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The second layers are generally one quarter wavelength optical thickness at a particular tuned wavelength , whereas the first layers are generally { HEAD ~ a plurality } of { TAIL ~ quarter wavelength optical thicknesses }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL