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