What Is the Trough of a Wave?

Video Transcript

"Hi, I'm Steve Jones, and I'm going to tell you about the trough in a wave. Well, obviously we have to have a wave before we start, so what is a wave? A wave is something that looks like this, and we, familiarly, see waves in the sea or waves in a cup when you drop something into it. These waves have peaks; that is, places where the wave is actually high, or troughs where the wave is actually lower, so the trough of a wave is the point where a wave is at its lowest. So, there is a trough, and here is a trough, and in fact, you can see that the length of the wave, the distance between two troughs or two peaks, is what we call the wavelength. So, the trough of the wave is where the wave is smallest. Now, this doesn't just happen in the case of water waves. This is an example, maybe, of a water wave, but in electromagnetic radiation we also have peaks and troughs, and therefore, we get some very strange things happening when, for example, the trough of one wave; let's say it here, meets the peak of wave number two. And you can imagine here is that the waves cancel each other, and if the waves cancel each other we get no wave. So, this is a very important property of waves, and if we don't know what a wave trough is and a wave peak is we can't understand the ideas of what we call interference. So, the trough of a wave is where the wave is at its lowest point."