 This website provides an interactive computer simulation of a ripple tank. You see, scientists know mathematical formulae for these waves and they can use these formulae to create computer images on your screen of what you would see in a real ripple tank. That's helpful as we don't have to construct ripple tank to explore waves. Let's use this site to simulate a planar wave. This is what the surface of the water would look like on a 3D view if we generate planar waves. I can re-orient myself in 3D to see what the waves look like. This is a projection of a three-dimensional planar wave into two dimensions. Remember that the dark regions are the crests. We can freeze the wave motion and identify some features of the wave from this projection. Again, the dark regions or lines are the crests and the distance measured between crests or lines is the wavelength. Because this is a projection of a wave onto two dimensions, we cannot distinguish the amplitude or height of the wave. The lines are referred to as wave fronts. Wave fronts will be helpful when we look at how waves interact with walls and objects. Now if you're at the ocean, you will no doubt see that the crest to crest distance is not a constant. It varies. You note that the period is not constant. Sometimes two ocean waves come within a short time. Sometimes you have to wait a bit longer for the next wave. Also, the amplitude or wave height is variable. That's because there are other factors affecting water waves. Changes in wind speed and direction, the slope of the beach. It's important to realize that this is an idealized model of a wave of a single wavelength, frequency, and amplitude. But it's fundamental to our understanding of how many different kinds of waves behave. So I've given definitions of characteristics of an idealized wave. Next time we discuss what these transverse waves carry and introduce another type of wave, the longitudinal wave. We've mentioned that sound, electromagnetic radiation, light are waves or have wave-like characteristics. And we'll talk more about this a bit later.