# What exactly is meant by a phase in Quantum Mechanics?

1. Jan 8, 2014

### ASGTech

I understand this is probably a very stupid question to some of the people on here, but none the less i would still like to know. It hasn't been explained very well to me.
I have a vague understanding that it is a number that you collect for each possible path? Please correct/elaborate on this if possible?
I was also told the phase represents the position in the cycle of a wave, whether it is at a crest or trough or some precise position in between. How do find the position it represents and how can you label an infinite number of paths with phases? How do you find the position in the cycle of a wave?

2. Jan 8, 2014

3. Jan 8, 2014

4. Jan 9, 2014

### Zarqon

A phase of anything is one part of a periodic behavior. Take the moon phases as an example, it goes full - half - crescent - half - full , etc in a periodic manner, and a particular part of that cycle, say for example the full moon is a phase of the whole cycle. And roughly a month later the same phase happens again. The same is true for any periodic behavior, including waves, that go between crests and troughs. We then characterize a full cycle as a number, like 360 degrees or 2*pi radians, which gives us more accuracy in determining where in the cycle we are. The starting point is arbitrary, and we could for example choose a crest in a wave to correspond to 0 degrees, and from that it would follow that the trough would be at 180 degrees.

Waves are often encoutered in physics, especially in quantum physics, coming from the wave nature of objects, and when we talk about a phase angle here, we talk about exactly the same thing as I mentioned above: a particular part of a periodic behavior compared to a chosen starting/reference point.

I hope that somewhat simple/fundamental explanation helped.

5. Jan 9, 2014

### ASGTech

Thank you all for your Input ! I appreciate it.