{TAIL ~ The interface region} is, at least in part, transmissive of {HEAD ~ radiant energy} 
{ TAIL ~ The interface region } is , at least in part , transmissive of { HEAD ~ radiant energy }
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD