So, now what we’re going to do is that we’re going to take the string of the guitar, visualize the air parallely with the slinky as it compresses and gets pulled back, and see both as a graph, and watch what we observe. So the string of the guitar moves upwards, compresses air that’s equal to somebody pushing the slinky … Pushing in that way and that’s equal to somebody creating a pressure up in the air and that’s going to be represented with a little peak in the graph – as you can see. so the pressure peaks … And now the string of the guitar is going to get pulled back, in other words the pressure drops… In this way, the slinky is going to get pulled back again… So the compression of slinky has gone a little forward … The spring has gone a little forward… With the back a little more elongated … And that in the graph is represented as a dot – a trough… A ‘crest’ and a ‘trough’.
So what have we really shown here..? A pressure up and a pressure down and that’s the way of visualizing it and this is the way in which it will draw as a graph..
Now what’s going to happen if we repeat it again..? So your are going to get the string move forward again, so one more compression, one more up. So you will let this run through time and that’s what you ‘ll observe… right ? The string compressing and refracting the air… compressing, pushing back… compressing, pushing back… So on with the slinky and so on with the graph.
The graph is a good way to visualize this… Rather a very very convenient way to visualize what’s happening for us… And you can also begin to observe that the graph is actually more suitable, more intuitive for the transfers here, right ? Because that’s exactly how… If you’ve set up a way with the string, it is exactly how it’ll develop… right? In this case to happens to be what we’re observing … Happen to be what kind of waves… That’s right… Longitudinal waves because the particles aware are pushing and they are compressing that much… So each particle is aware what it’s really doing … It’s just moving away from its position and coming back… Is oscillating back and forth about its position.. This way and the sound itself is moving in the same direction, therefore it’s a longitudinal wave.
So longitudinal waves are usually a little difficult to visualize… Therefore the graph actually gives you more of a transverse representation of it. Because if you have taken a string and done that… That’s the graph is how to develop… But in this case that represents the sound and the slinky both of which are longitudinal waves.