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