I have followed some of the previous posts on the topic , but the conflicting arguments have left more than confused. Consider this simple scenario : Two wave pulses on a string generated by identical sources but with a phase difference of 180 degrees meet and interfere destructively. For simplicity, lets assume that their amplitudes are the same. Where does the energy of the two wave pulses ( 2*Asquared ) go in the moment when the amplitude of the disturbance on the string is zero. Possible explanations I have received for this are : 1) The energy is absorbed by the source. 2) Stored in the potential energy of the string as it is disturbed by two displacements in the opposite sense. 3) Energy is not a local property , and it remains conserved over time in this case ( after the waves separate ) Personally, I find the second argument the most appealing, but I'd like to be sure ... which is it? Any help would be greatly appreciated.