0:05 → 0:08
Waves transfer energy from one place to another.
0:08 → 0:16
You should already know how to describe them in terms of frequency, wavelength and amplitude, which we looked at in another video.
0:16 → 0:21
In this video we're going to look at two ways they can be classified.
0:21 → 0:28
Waves are produced as a result of vibrations and can be classified as transverse or longitudinal.
0:28 → 0:35
Whether they are transverse or longitudinal depends upon how the particles are made to vibrate as the energy passes.
0:35 → 0:38
Let's look at longitudinal first.
0:38 → 0:44
This is where the particles vibrate parallel to the direction in which the wave of energy is traveling.
0:44 → 0:49
Notice that the ends of the slinky don't ever leave the hands holding them.
0:49 → 0:51
It's only the energy that travels.
0:51 → 0:56
The places where the coils or particles are bunched together are called compressions.
0:56 → 1:02
Where they are furthest apart are called rarefactions.
1:02 → 1:05
An example of longitudinal waves is sound.
1:05 → 1:11
When a drum is struck the drum skin vibrates, which causes the air particles next to it to vibrate.
1:11 → 1:21
This causes the next air particle to vibrate, then the next, and so on until the vibration reaches the ear causing the eardrum to vibrate.
1:21 → 1:26
The vibrating air speeds away from the source, creating a sound wave.
1:26 → 1:29
Let's look at another type of wave: transverse waves.
1:29 → 1:36
The hand moves up and down, as does the slinky, but the wave itself moves from left to right.
1:36 → 1:41
So the particles vibrate at 90 degrees to the direction that the energy is moving.
1:41 → 1:48
We can simply think of it as in longitudinal waves, the hand pulses horizontally, pushing and pulling,
1:48 → 1:53
and the wave energy also moves horizontally, back and forward.
1:53 → 2:00
Whereas in transverse waves, the hand moves up and down, but the wave energy still moves horizontally.
2:00 → 2:04
Again, the ends of the slinky never leave the hands holding it.
2:04 → 2:06
It's just the energy that moves along.
2:06 → 2:10
Transverse waves are usually used to show the wavelength and amplitude.
2:10 → 2:19
Pause the video and see if you can remember how to label the amplitude and wavelength on the diagram.
2:19 → 2:22
Did you get them right?
2:22 → 2:26
The waves on the surface of water are transverse waves.
2:26 → 2:29
They make the water surface go up and down.
2:29 → 2:35
All types of electromagnetic waves, like visible lights, are also transverse waves.
2:35 → 2:42
So now you should be able to describe the differences between transverse waves and longitudinal waves.
2:42 → 2:48
Remember: it is the energy and not the slinky itself that travels.