Mechanical and Electromagnetic Waves

101 - Mechanical and Electromagnetic Waves

In this video Paul Andersen compares and contrasts mechanical and electromagnetic waves. Both types of waves transfer energy through oscillations but mechanical waves requires a medium. Several examples of each type of wave are included.

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Music Attribution
Title: String Theory
Artist: Herman Jolly

All of the images are licensed under creative commons and public domain licensing:

[anime_stui]

This was posted half a decade ago but it still helpful til this day. Thank you very much!

[Firedemon]

A good way to contrast Mechanical and Electromagnetic waves is to figure out, can they be transmitted through space? Through an area where there’s no medium or no matter? An example of electromagnetic waves that we can see, are explosions on the moon. The moon keeps getting hit by meteors, and there are little flashes of light that NASA’s been monitoring. One, in 2013, was so bright, you could’ve seen it with the naked eye. Now, that flash is moving towards our eyes through space; it’s electromagnetic. But it’s also producing mechanical waves. So we would have seismic waves on the moon. If you were on the moon, you could feel those, the vibration through the moon’s surface itself, but since there’s no air around the moon 一 not atmosphere, you wouldn’t hear any sound. And in fact, if the moon were to explode, if you were to look at it in space, it would be totally silent. You could still see it, because that’s electromagnetic waves. And so, energy is transferred through waves. Those waves can be mechanical, or electromagnetic. Mechanical are ones that require a medium, or some material or matter to move through, electromagnetic don’t. No medium required. An example of a mechanical would be sound waves, example of electromagnetic would be light. And so mechanical waves require some sort of medium to move through. So as you move your hands across the surface of water, water is the medium. You’re oscillating the surface, and that energy is being transferred through the medium of the water itself. An example could be ocean waves. Sound waves work the same way, you can’t see it, but there are air molecules, and so as I speak, I’m vibrating the air molecules, that vibrates the microphone, which vibrates your speaker, which vibrates the air around your ear, and so you can hear it. If there’s no gas molecules around your ear, then you can’t hear it. An example of mechanical waves are seismic waves; those that are produced after an earthquake, and this is a really cool study. So this was in 2011, there was an earthquake in Virginia. And they were monitoring twitter, and looking for people who tweeted the word, “earthquake.” And they just kept track of where those tweets were, and how long it took for them to reach those people. So you can see the seismic waves are actually moving out. You can trace where the earthquake went. Now, what’s interesting, is that twitter uses electromagnetic rays, so it’s using electricity to transfer those messages, and so the U.S. geologic service is looking at twitter as a way that we could have an early warning system, so that we could pick up, and protect ourselves before those mechanical waves reach us. An example of mechanical waves that we’re all familiar with is sound waves. So when you hit a bass drum like this, it’s very loud, but what you’re really doing is vibrating the surface of the drum, and that’s vibrating, if we look at it, it’s vibrating all the air molecules around it. And so we have these longitudinal waves that move out in a three dimensional sphere, and away from that bass drum. So that’s vibrating your eardrum, and that’s what you perceive as sound. Now electromagnetic waves are different, if we look out into space, there’s no medium there; there’s no matter, but we’re getting light from these distant stars. And so light, or radio waves, can travel through nothingness. Now they can still move through mediums, so for example, light is moving through your room, where there’s gas, or could move through a prism, we could break it into its electromagnetic waves, so we could see the different colors inside white light. But it can still move through nothingness. A good example of that would be using a vacuum pump. So if we were to put an alarm clock inside a vacuum pump, and we just have the alarm go off. And so the way this works is it vibrates back and forth, and you could ring the bells back and forth, like this, but let’s say we started to remove the air from inside the vacuum. What would happen as we pump the air out? You would still be able to see the vibration in the alarm clock, because that’s electromagnetic waves, but pretty soon, all of the gas would be gone. There would be no more sound waves being produced, and you wouldn’t hear anything. And so, did you learn to describe sound as a transfer of energy through a medium? And then, can you contrast mechanical, which require a medium, and electromagnetic waves, which don’t? I hope so, and I hope that was helpful.

[savagepro]

Today, February 13th, 2023, I searched the whole frekin internet looking for a simple explanation for mechanical and electromagnetic waves, and I arrived here. Heaven!

[lyndamccroskey]

(Professor of stats) This series is well done! I like and recommend these to my students in social science. Great ancillary to any quality textbook and course lecture/materials.

[michaelryd]

A medium does not have to be matter in the ordinary way, plasma or particles will due. Density of the medium is the factor that determines if you will se or hear the wave or not!

[ryanmaina]

Thank you very much, this helped me alot

[neilkannan]

rlly helped, i had no idea what mechanical waves were!

[nitintripathiiii]

How is it possible to move anything without a medium..even if i say about a magnet. What is the phenomenon of attraction and repulsion without considering the charge.And if there is a charge it must have some weight and will require a medium to propagation of these magnetic waves!!

[xiiixiiih.]

Is the word meadium , a type of phone operator?🥺in a way

[jsdsparky]

In the case of electromagnetic waves, I just can't conceptualize a wave propagating without anything moving. What is physically oscillating?

[Jarrod_C]

Well what about the dark matter in space? So can we truly say there is nothingness? I think there may be a different type of medium in space that is unique to space only and not necessarily nothing.

[dipalikshetraphal]

Thanks for providing this video. Need more details about waves as energy. TW and LW properties etc..

[keawetone]

just seems like a nice guy so i listened to this video

[malipetek]

EM and physical wave distinction feels immature. Waves are not of a type of existence they are type of energy bursts that get away from source to reach equilibrium and their ability equate their energy with surrounding medium is dictated by its frequency.

[alrayyaniQtr]

Can i think of electromagnetic waves as being independent and mechanical waves being dependent?

[AshleyMires]

Is their absolutely NO atmosphere in space? Or is it just no inefficient we look past it?

[yeetboygocrazy]

Dude how many bees have stung you in the jaw this month XD

[urmommywommy]

this is the guy who has been stalking me for 3 years, he was arrested because i claimed a restraining order against him but he came into my house.

[Cadeniplier]

You Don't look like a Mr. Anderson... :\

[shraysls]

Not much I want to know more about electronic wave n what limit of E-wave.