In diffraction, light acts as a wave, bending around an obstacle in {HEAD ~ its path}, such as {TAIL ~ a grating} 
such as
In diffraction , light acts as a wave , bending around an obstacle in { HEAD ~ its path } , such as { TAIL ~ a grating }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL