# eli5 wtf is phase difference

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The phase is where the wave is at, so if you do a sine wave with your finger you’ll move it up then down then up in an oscillating pattern. The point where the finger is along the wave is the wave’s phase.

Now do another different wave with your other hand and start moving both of them.

Stop and superpose the fingers. The difference between the fingers’ heights is the phase difference

If you have two waves oscillating with the dame frequency, they can either be in phase or out of phase.

If their crests and troughs line up together, they’re in phase. If the crests of one line up with the troughs of another, they are 180° out of phase. Anything in between is still out of phase, but by a different amount. 3 phase power for example has 3 different waves of AC power, but all 120° out of phase with each other. If you have the equation of two waves, the difference of their phase shift constants would be how far out of phase they are

Given two waves of equal frequency, if their peaks and valleys align with each other, then the waves are in phase, otherwise the waves are out of phase.

Phase difference simply means the magnitude of the distance between corresponding peaks or valleys.

Since waves are cyclical, they can be expressed in terms of their relationship with a [unit circle](https://www.mathsisfun.com/algebra/trig-interactive-unit-circle.html). Therefore, phase difference can be expressed as an angle. Where two waves are in phase, their phase difference is zero degrees. If waves are fully out of phase (meaning one wave’s peak coincides with the other wave’s valley) then they are 180 degrees out of phase.

If you have two waves oscillating with the same frequency, they can either be in phase or out of phase.

If their crests and troughs line up together, they’re in phase. If the crests of one line up with the troughs of another, they are 180° out of phase. Anything in between is still out of phase, but by a different amount. 3 phase power for example has 3 a different waves of AC power, but all 120° out of phase with each other. If you have the equation of two waves, the difference of their phase shift constants would be how far out of phase they are.

Imagine you and your friend have synced breathing. You both start inhaling at the same moment, and exhaling at the same moment. You have the same frequency, and assuming you breathe in the same volume, then also the same amplitude. Because of the synchronization, also the same “phase.” Let’s call the moment you start inhaling, phase 0, when you finish inhaling, phase 180, which is also when you start exhaling, and phase 360 when you finishing exhaling and start inhaling again. If you friend now starts to inhale when you start to exhale, then when you’re at phase 0, they’re at phase 180. You’re out of phase. The phase difference is 180, which is half of 360, half the cycle. So you’re totally out of phase, opposites, antiphase. If they starts inhaling halfway during your inhalation, that’s 90 phase difference. And so on.

Now consider air volume in your lungs as a variable. If you plot it, you see it going up when you inhale, down when you exhale, a cycle that looks like a wave. Now you can apply this to any wave.