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So this is basically What happens to the energy when waves perfectly cancel each other? again, but I'm not understanding the answers given (or they don't address what I am confused about)
Basically given that waves can be reflected one could conceivably reflect two waves so that perfectly cancel each other out (I do not mean standing wave, I mean reflected so they end up going in the same direction and are "off" by exactly half a wavelength) Suppose that we have 2 sources of same frequency light aimed directly at each other call this line l horizontal, and let P be a plane containing l and consider a perfectly reflective square (or cube ) S contained in P oriented 45 degrees to l and intersecting l on 2 adjacent sides of S so that the 2 light sources are perpendicularly reflected (in same direction) now slide the square S perpenticularly to l so that l intersects l at a single point p \in l. Now we have a way to "combine" 2 waves that are not in the same direction and we can choose p so that the two waves are "precisely" out of sync and cancel perfectly. Of course I mean ignoring quantum / wave particle duality loss of heat/friction etc Perhaps one should visualize this instead as sound waves bounced perfectly so they cancel out or..

@ACuriousMind while this could just be a comment on a different thread my comment did not recieve any attention, thus I decided to make it another topic

Hao S
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  • That is what an opaque screen does: on the other side, the field is the sum of the incident field and the induced fields from the electrons in the screen 180 degrees out of phase with the incident field. The result is darkness. The screen gets warm (or in case of a mirror, there is also a reflected field). –  Jan 02 '19 at 22:10
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    In engineering (specifically: ship engineering) there is a design whose function involves destructive interference: bulbous bow. A fast moving ship generates a pattern of surface waves: the bow wave. From the Wikipedia article: "A bulb alone forces the water to flow up and over it forming a trough. Thus, if a bulb is added to a conventional bow at the proper position, the bulb trough coincides with the crest of the bow wave, and the two cancel out, reducing the vessel's wake." – Cleonis Jan 02 '19 at 23:01
  • Your question was labeled as a duplicate, but in my opinion your question is in fact not a duplicate. Perhaps you can use the above bulbous bow example as a starting point for a new question, and make it as distinct as possible from the suspected duplicate. – Cleonis Jan 02 '19 at 23:04
  • @Cleonis I don't know much about physics or engineering, but assuming perfectly reflective frictionless ... etc in my above question why doesn't this violate conservation of energy? – Hao S Jan 02 '19 at 23:22
  • @Pieter what is a reflected field? also how would the heat be created? theoretically if two light waves interfered in a vaccum where could the energy go? (I'm assuming one could either create a wave at a point going in one direction while being "transparent" or reflect without any loss of energy) – Hao S Jan 05 '19 at 06:02

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