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