What is Interference?
[[File:Interferenz.jpg|right|thumb|200px|When two rocks hit a pond at the same time their waves interfere with each other]] In [[physics]], '''interference''' is the effect of [[wave (physics)|wave functions]]. A single wave can interfere with itself, but this is still an addition of two waves (see [[Young's double-slit experiment|Young's slits experiment]]). Two waves always interfere, even if the result of the addition is complicated or not remarkable. Something that happens when two or more [[waves]] are in the same space. Sometimes the peak of one wave joins with the peak of another wave, so the resulting peak is twice as high. Sometimes the peak of one wave falls into the trough of another wave, and the surface is then flat. When waves add their effects, it is called positive interference, or constructive interference. When one wave subtracts from the effects of the other, it is called negative interference, or destructive interference. If two people pushed on a car in the same direction, they would move the car better than either one alone. That would be positive interference. If two people of equal strength pushed the car from opposite directions, then it would not be moved by either of them. That would be negative interference. ==Constructive interference== [[File:Destructive interference1.svg|thumb|200px|''Destructive interference'': When the top of one wave meets the trough (bottom) of another wave in the middle, the water stays flat.]] {{stack|[[File:Constructive interference.svg|thumb|200px|''Constructive interference'': When the tops of two waves meet in the middle a taller wave is seen.]]}} Constructive interference happens when two or more waves are in the same space and in [[phase]]. When this happens, the waves' amplitudes add together and the total is greater than the [[amplitude]] of any of the waves by themselves. This causes the waves to appear more intense. At time = 0, one wave top is moving from the left and another wave is moving from the right. <br> At time = 1, the two wave tops