When waves interfere with one another there are two types of interference, constructive and destructive.
Constructive Interference occurs when waves combine to create a wave with a larger amplitude. When the crests of two waves come together they form a higher peak. Troughs coming together form a deeper trough. Higher peaks and deeper troughs are both examples of increasing the magnitude of a wave.
Destructive Interference is when waves coming together interfere with one another in a way where energies are subtracted. When the crest of one wave overlaps with the trough of a different wave. With destructive interference if the crest is a greater amplitude than the trough, the part of the crest bigger than the trough will remain. If the amplitude of the crest of a wave is equal to the trough of a wave, they will cancel each other out.
