In some embodiments, multiple portions of {TAIL ~ surface} 501 are simultaneously exposed to {HEAD ~ the electromagnetic radiation} 
In some embodiments , multiple portions of { TAIL ~ surface } 501 are simultaneously exposed to { HEAD ~ the electromagnetic radiation }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD