Wave interference happens when two waves overlap to form an interference
pattern. The amplitude of the resulting wave may be increased,
decreased or neutralized.
Overlapping waves can create two types of interference. The interference could be a constructive interference or a destructive interference.
Constructive interference occurs either when one crest of one wave overlaps the crest of another wave or the trough of one wave overlaps the trough of another.
After the two waves above interfere, they will form a constructive interference.
They will then create the resulting constructive interference wave
shown in orange below.
Notice that the height of the orange crest is as high as the height of the blue crest + the green crest.
By the same fashion, the height of the orange trough is as high as the height of the blue trough + the green trough.
Destructive interference occurs when one crest of one wave overlaps the trough of another wave. In this case, the waves are out of phase with each other.
If you keep moving them toward each other, you end up with the graph above. If the height of the crest is the same as the trough after the interference, there will
be a cancellation or neutralization.The cancellation is shown with a red line and a brown line.
Sometimes a little height is added or removed. It depends on the situation. This is illustrated in the image to follow.