Physics Unit 9

We started Unit 9 today, which was both interesting and incredibly painful. This unit is focused on waves and sound, although we haven't really covered much of sound yet. We pretty much spent the whole day learning about waves, how to graph them, the different parts of them, and so on.

The picture on the left is a wave. A wave is a vibration in space, and a vibration, is pretty much a wiggle in time that moves back and forth between points. Anyway, there are many different parts of a wave. There is a thing called a loop, which is pretty much the curve of the wave. In this picture, there are three loops. There is also the crest, which, as shown in the picture, is the top part of the loop, while a trough is the bottom part. Both the crest and the trough are antinodes, which are the parts of the wave that move. A node, on the other hand, is the part of a wave that doesn't move, which is located in between the loops of a wave. Next, there is the amplitude. An amplitude is the distance between a crest and the equilibrium point of the wave, or the trough and the equilibrium point. Lastly, there is a thing called a wavelength. A wavelength, is measured from two identical portions of the wave. As you can see in the picture, the wavelength starts at an equilibrium point and ends at the next equilibrium point where the wave is travelling in the same direction, in this case, down. An easier way to find the number of wavelengths a wave has, is to count the number of loops the wave has, and divide it by two. In this case, there are three loops, so there are only one and a half wavelengths.

Here is some more important vocab we learned:
Medium = the thing that carries the wave
Period = the amount of time it takes for one complete cycle to occur
Frequency = ƒ = how many cycles pass in a second. Unit = Hertz (Hz) = 1 cycle ÷ second
Transverse waves = when the wave energy moves perpendicular to the wave velocity
Longitudinal waves = waves in which the energy moves parallel to the wave velocity
Principal of Superposition = says multiple waves can exist in the same space
Constructive Interference = if waves collide with each other and are both positive or both negative, they will create a loop twice as large as their original size. However, if a positive and a negative wave collide, their opposite forces will cause a flat wave.