Waves
an introduction
What are waves?
That is the question we will address in this following section.
Waves are the transition of energy. While it may look like the wave is causing the object to move towards you it is only the wave that is moving. The energy is the only thing moving. If you placed a buoy on the water and watched it the buoy would not move closer to you. Why? Well it is because the energy is what is traveling towards you, it will make the buoy move up and down but it wont make the buoy get closer to you.
"But then why do you move towards the shore when swimming in the ocean, it's the waves that push you!" True you are moving because the wave itself but not because the wave is moving you, gravity is. As you lift up you begin to fall down the hill the wave formed. You are just falling constantly because the wave is pushing you up as you fall. In the end the only thing the wave itself is transmitting is energy, not matter.
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click on the camera for a video
This is what a transverse wave looks like, note that it is made by the medium vibrating perpendicular to the direction the wave is moving. What does that mean? As you see the wave defects up and down but the wave is actually traveling to the right.
The up and down arrow represents the amplitude.
The left and right arrow represents the wavelength.
Another thing to note is the equation for a wave. v = λf
v represents the velocity of the wave, it is how fast the wave is traveling through the medium. Its units are a distance over time (m/s)
λ (lambda) This represents the wavelength, its units are a distance (km, m, mm, nm, ...)
f This represents the frequency. Its unit is Hz or 1/s
Transverse waves are associated with light.
A longitudinal wave is associated with sound. These waves travel in the same direction they are vibrating. Imagine a line of people. If you pushed the person in the back you would see a moving wave as people bumped into each other. (Then you would see a fight so don't do it)
The longitudinal wave has different names for the parts of the wave.
Compression
Rarefaction
Another thing to note is the equation for a wave. v = λf
v represents the velocity of the wave, it is how fast the wave is traveling through the medium. Its units are a distance over time (m/s)
λ (lambda) This represents the wavelength, its units are a distance (km, m, mm, nm, ...)
f This represents the frequency. Its unit is Hz or 1/s
You have all heard the Doppler effect at least one time in your life.
(click the arrow to stop the sound.)
It is when you have a sound source moving past you. As it approaches the wavelength shrinks, causing the frequency to get higher. As it passes you the wavelength gets stretched out causing the frequency to drop lower.
The equation is
Fd = Fs ( v-vd / v-vs)
There are 2 types of interference:
Click on the camera for a video
Constructive is when 2 waves with the same sign on their amplitude merge to create a larger wave. Think about when you 'construct' a building, you build it up just like the waves are going up.
Destructive is when 2 waves with opposite signs on their amplitude merge to reduce their amplitude. Think about destruction, you brake things down to smaller pieces. The wave here is being made smaller.
Reflection is when the wave Bounces off a surface
Refraction is when the wave Bends by passing through a medium
Diffraction is when the wave Bends around the medium
