racted wave changes as it spreads out. They both actually decrease because the wave tries to cover more area. The direction of the wave changes because the wave appears to spread out. Why does this stuff occur? It is because a wave is made up of a bunch of point sources all in a straight line, moving at the same velocity. The wall and the wave stop when the wave hits the barrier, all but one or two of the point sources ceases to really become a wave, but it becomes a point source, which explains all of the other observations. Diffraction proves the idea that a wave is made up of a bunch of point sources.The fourth type of wave phenomena that we will look at is interference. Interference is having two or more waves acting on the same medium at the same time. To observe interference in the ripple tank, we simply put two point sources in the tank, each individual making waves that go out in concentric circles around the point source. However, the interference occurs when the two circles of waves hit and change each other. The only variable that changes in interference is frequency and amplitude. Every other variable, velocity, direction, and wavelength, stays thesame. What seems to occur, is that when these waves cross, they may do one of two things. They may merge into one bigger wave, through a term called maximum constructive interference in which two waves are combined into one bigger wave. The other thing that may occur is that the two waves will cancel each other out, making a area of the tank where there appears to be no waves at all. When this happens, it is called complete destructive interference. These two ideas occur for one reason. When the waves cross, they either merge with the other wave, or cancel it out, depending on its wavelength. This is the reason for the areas of calmness (called the lines of reinforcement), and the area o the heightened waves. Interference is having two or more waves acting on the same medium at the...
