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Wave Velocity

by Jared Rovny
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    00:01 This wave velocity has a few properties that might seem counter intuitive at first.

    00:05 One of which is that the velocity is only determined by the medium that the wave is traveling through, whether that's water or whether it's sound waves through the air.

    00:13 It's only determine this velocity by whatever medium the wave is traveling through.

    00:19 It could also be determine by properties of that medium.

    00:22 So it could be determined for example by the density of the medium or in some cases by the temperature that that medium is at.

    00:27 And the reason for this is that the wave as it's traveling through the medium, you can't push it to make it go faster or try to be moving as you create the wave in order to speed up your wave because the only way this wave is moving is by the communication between different particles or different object in your wave.

    00:46 So for example for a water wave you just have different water molecules and they are bumping into each other and the rate at which these are bumping into each other and transferring this energy, it's not something you can determine just in the way you create the wave.

    00:58 And so this again it's only going to be determined by the velocity, will only be determine by the properties of the medium it's traveling through.

    01:06 If your wave goes from one medium to another medium.

    01:11 So for example if a light wave is going from air and entering into water or even a sound wave is trying to travel from water and enter into the air.

    01:19 The frequency will not be changed as the wave goes from one medium to another but the velocity and the wavelength of your wave can change.

    01:28 The way to remember that the frequency won't change as your wave enters a new medium is maybe best to imagine for yourself the wave as it's crossing this boundary or this threshold.

    01:38 Whatever is causing the wave to oscillate and move as it's entering this new boundary, we'll still be causing a way to be moving on the other side of that boundary.

    01:47 And so the rate of this motion has to be the same, the frequency has to be the same.

    01:51 But the other physical properties of the wave, can't change like as we discussed the wavelength and the velocity of the wave.

    01:58 We have a couple of examples of types of waves and we'll discuss both of these in more detail but just so we can put something a little more concrete to the things we've just discussed.

    02:08 Sound, would be a good example of a wave and sound has a wave of pressure.

    02:13 Its pressure as you watch the air pressure move, created by any sort of moving object.

    02:19 So we'll discuss a little bit later that, for example if we play a string on an instrument, it's pushing the air and then pulling the air and pushing the air and that causes these waves of pressure to go through the medium which in this case is just the air.

    02:33 Light is also a wave and since we've just discussed electromagnetism, we could say that it is an electromagnetic wave and so the electric field and the magnetic field, we talked about how moving charges create magnetic fields and it turns out there's this interplay of the electric and magnetic fields creating each other and so we have a wave, an electromagnetic wave that propagates at a particular speed, the speed of light and light is also a wave for this reason.


    About the Lecture

    The lecture Wave Velocity by Jared Rovny is from the course Periodic Motion.


    Included Quiz Questions

    1. It depends only on the medium it is traveling through
    2. It depends only on the frequency of the wave
    3. It depends only on the wavelength of the wave
    4. It depends only on the period of the wave
    5. It depends only on the amplitude of the wave
    1. Frequency
    2. Amplitude
    3. Wavelength
    4. Velocity
    5. Distance between peaks

    Author of lecture Wave Velocity

     Jared Rovny

    Jared Rovny


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