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