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