If you hold the guitar up toward the tv, to where your line of sight sees the guitar string first and the tv in the background, you should pluck a string. You can actually see the wavelength of the vibrating string at whatever note you’re playing. Try changing the note (ie finger the first fret, then the second fret, then try other stings). This is really cool.
You probably know something about waves, and the common analogy to picture waves is to compare them to waves in bodies of water, like the ocean or a swimming pool. Using the guitar string, you can actually get a pretty clear picture of a real wave happening, and you can hear it on top of seeing it.
It’s really worth a shot. Just remember to check it out if you’re near a guitar and a tv. Of course, make sure the tv is on when you do this!