Lets consider two waves, the intensity of each wave is proportional to the square of their amplitude, now why the intensity of the sum of the two waves is not the sum of each intensity but is proportional to the square of the sum of the amplitudes? (i know it on the math side and i can demonstrate that but i don't get the physical meaning of that) Whats the meaning of that? Why is the intensity of the result wave different from the sum of the intensity of the waves? Does this mean that there's a difference between the intensity of two waves and the intensity of the resultant wave, but why this happens? There are points where the sum of the amplitude is zero then there is no intensity, and others where the intensity is even greather than the sum of the intensity of each wave, i can't get why, doesn't this violate the energy conservation?