▁side . ▁( See ▁image ▁at ▁top .) ▁ ▁W ave ▁diff raction ▁vs . ▁wave ▁inter ference ▁With ▁regard ▁to ▁wave ▁super position , ▁Richard ▁Fe yn man ▁wrote : ▁ ▁Other ▁authors ▁elaborate : ▁ ▁Yet ▁another ▁source ▁conc urs : ▁ ▁W ave ▁inter ference ▁ ▁The ▁phenomen on ▁of ▁inter ference ▁between ▁waves ▁is ▁based ▁on ▁this ▁idea . ▁When ▁two ▁or ▁more ▁waves ▁traverse ▁the ▁same ▁space , ▁the ▁net ▁amplitude ▁at ▁each ▁point ▁is ▁the ▁sum ▁of ▁the ▁amplit udes ▁of ▁the ▁individual ▁waves . ▁In ▁some ▁cases , ▁such ▁as ▁in ▁noise - can cell ing ▁head ph ones , ▁the ▁sum med ▁variation ▁has ▁a ▁smaller ▁amplitude ▁than ▁the ▁component ▁variations ; ▁this ▁is ▁called ▁destruct ive ▁inter ference . ▁In ▁other ▁cases , ▁such ▁as ▁in ▁a ▁line ▁array , ▁the ▁sum med ▁variation ▁will ▁have ▁a ▁bigger ▁amplitude ▁than ▁any ▁of ▁the ▁components ▁individually ; ▁this ▁is ▁called ▁construct ive ▁inter ference . ▁ ▁Depart ures ▁from ▁linear ity ▁In ▁most ▁real istic ▁physical ▁situations , ▁the ▁equation ▁gover ning ▁the ▁wave ▁is ▁only ▁approximately ▁linear . ▁In ▁these ▁situations , ▁the ▁super position ▁principle ▁only ▁approximately ▁holds . ▁As ▁a ▁rule , ▁the ▁accuracy ▁of ▁the ▁approximation ▁tends ▁to ▁improve ▁as ▁the ▁amplitude ▁of ▁the ▁wave ▁gets ▁smaller . ▁For ▁examples ▁of ▁phen omena ▁that ▁arise ▁when ▁the ▁super position ▁principle ▁does ▁not ▁exactly ▁hold , ▁see ▁the ▁articles ▁non linear ▁opt ics ▁and ▁non linear ▁ac oust ics . ▁ ▁Quant