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