I thought that today's class was one of the more interesting ones.  We learned all about waves energy.  At first I thought that I already knew about wavelengths from chem and math.  However, even though there was some overlap, I learned a lot of new things.  I knew nothing about pulses and nodes, and I had no idea that wave velocity stays constant.  I also didn't know the ways waves and pulses colliding interact with each other.  This is the principle of superposition.  The picture above has an example of a pulse.  If another pulse were to collide with it from the opposite direction on the same side of the string, the moment when the pulses collide would create an even bigger pulse.  If the opposite pulse were to be on the opposite side of the string, the string would flatten as the pulses collided.  One of the more interesting things I saw today was the way the frequency of the strobe light changed the way we saw the fan.  I never realized the blades of a moving fan could appear as anything other than a blur.