Today, I'm going to be talking about the Physicsy kind of waves- what a wave IS, the two types of waves, the 5 main properties of waves, and electromagnetic waves.
First off, what the heck IS a wave?
Essentially, a wave is ENERGY. Nothing more, nothing less. A wave is energy that is transmitted from one point to another through a medium- i.e. THROUGH something. That medium can be practically anything, from air (say "heloooooooooooooooooooo") to water (glugglugglug) to an electromagnetic field (more on that later on).
Every wave forces particles to move- a wave transfers energy to particles in its way. Waves can be classified to two ways based on HOW they force particles to move. A wave is either transverse or longitudinal based on how they force particles to move.
In a longitudinal wave, the energy forces particles to move in the direction of the wave's travel. Longitudinal waves cause compressions and rarefactions- basically, the medium has a higher density in a compression and a lower density in a rarefaction. The diagram below represents the density of the medium at any given point.
In a transverse wave, the energy forces particles to move up and down- this is perpendicular to the direction the wave is traveling. Transverse waves are made up of a series of crests and troughs (See below)
Whoa, hang on! How can BOTH the waves be perpendicular to the wave's direction of travel?
The answer: The waves travel in 3-dimensional space. Imagine a three-dimensional coordinate plane (with an x, y, and z-axis). x is length, y is height, and z is depth. Our electromagnetic wave is traveling along the x-axis.
The relation between any two of the three axes is that they are perpendicular to each other. For example, the x-axis is always perpendicular to the y-axis.
So, if a wave is traveling along the x-axis, its direction of travel is PERPENDICULAR to the y-axis AND the z-axis. This is how electromagnetic waves exist- both parts of the wave are perpendicular to the direction of the wave's travel, but along different axes.
Waves have 5 essential properties- every wave does all five of these things. I'm going to go over the simple ones really quickly so I can get to the more complex stuff.
1. Reflection: Basically, when a wave hits an obstacle, part of the wave's energy is reflected back. Best examples: Mirrors and echoes. If you're standing at the edge of the Grand Canyon and yell down, you hear an echo. When the sound wave hits the rock at the bottom of the canyon, part of the soundwave is reflected back to you.
2. Transmission: When a wave hits an obstacle, only PART of the wave's energy is reflected back. The rest of the wave's energy is transferred to the new medium (aka the obstacle). Example: If you're under water, you can still hear someone talking above the surface of the water.
3. Refraction: When a wave transmits part of its energy to a new medium, the wave changes directions. Example: Have you ever stuck a pencil/straw in a glass of water? The pencil looks like it bends at the water's surface.
4. Diffraction: When waves meet an obstacle, they move around it. Plain and simple. Does this seem to conflict with points 1&2 (reflection and transmission)? Why would a wave reflect off an object or pass through it if the wave could just go around? The answer: Diffraction DOES occur for large objects, but not to a very large extent. Diffraction is only noticeable with relatively SMALL obstacles. Example: You can hear a violinist play even if said violinist closes the door.
5. Superposition: When two waves traveling through the same medium collide, they affect (interfere with) each other- but only while the two waves are in contact with each other. Once the two waves separate, they have no further effect on each other. There are two main types of superposition: Constructive and Destructive interference (saved for next post :) )
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