Hello!
The type of interference that increases the energy of the resulting wave is called constructive interference. The type of interference that results in a loss of energy is called destructive interference.
When two or more waves are in the same medium, they can cross at a given point, where interference happens. When the two waves are in phase, the resulting amplitude in the point of interference is maxed. This is called constructive interference.
When the two waves are in opposing phases, the resulting amplitude in the point of interference is minimized. This is called destructive interference.
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