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Old Dec 25th 2015, 05:26 AM   #1
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Classifying waves

Hello, I'm trying to make it flow chart diagram to help understand wave types. I can't paste to flowchart on this forum but I've listed the items that were going to each box. Please can someone look at them and correct me if there are errors or add information where it is lacking.
Thank you very much.
Merry Christmas and happy New Year

Waves - longitudinal or transverse.

Transverse waves - mechanical transverse or electromagnetic transverse.

Mechanical transverse waves - surface water waves, wave on a rope, seismic S waves.

Electromagnetic transverse waves are visible light, gamma rays, radio waves.

Mechanical transverse waves require a medium for propagation (travel).

Electromagnetic transverse waves do not require a medium for propagation and can travel in a vacuum but also through a medium.

Longitudinal waves sound waves, seismic P waves, underwater waves

Longitudinal waves - require a medium
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Old Dec 25th 2015, 07:00 PM   #2
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Wave Classification

Hallo Hero and allow me to return your seasonal greetings.

Waves Long. or tran. .... yes.

Transverse Waves .... mechanical yes. E-m waves ...as you say do not require a medium and I think they need a little care in classifying them. Lacking a medium can you truly put thrm into a group of waves which "travel"?
What exactly do you mean by propagating when there is nothing present through which to propagate?

Which moves the problem on a step further ?
It is still too close to Christmas dinner but I would suggest that perhaps they go into a new box of their own?


All e-m waves go into the same box ?
BUT do they indeed travel IN a medium? They may indeed appear to enter SOME meedia and to re-appear on the other side - they even interact with a medium and get refracted - but ... ?

Your last two items illustrate my queries .

Do come back if I have dirtied the windscreen.

Ken Green
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Old Dec 26th 2015, 04:16 AM   #3
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Originally Posted by kengreen View Post

Transverse Waves .... mechanical yes. E-m waves ...as you say do not require a medium and I think they need a little care in classifying them. Lacking a medium can you truly put thrm into a group of waves which "travel"?
What exactly do you mean by propagating when there is nothing present through which to propagate?
Doesn't propagate just mean "to travel"?
That's what I thought it meant. He seemed to be suggesting that for a wave to be propagated, a medium a medium is doing the propagating (moving) of the wave.
All bit confusing BUT I have written that transverse electromagnetic waves do not require a medium in which to propagate; they can travel in a vacuum.
Have I got this right?


Originally Posted by kengreen View Post


... I would suggest that perhaps they go into a new box of their own?

All e-m waves go into the same box ?
BUT do they indeed travel IN a medium? They may indeed appear to enter SOME meedia and to re-appear on the other side - they even interact with a medium and get refracted - but ... ?
I've put transverse waves in their own box. Have a look please:


I've split waves into transverse (box 1) and longitudinal (box 2)

Box 1 (transverse) I split into box 1 a (mechanical transverse) and box 1 b (electromagnetic transverse)

Box 1B (electromagnetic transverse) I've said consists of (examples) visible light, gamma radiation, radio waves.

Box 1B (electromagnetic transverse) I've said can travel in any medium and even in the absence of a medium (vacuum)
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Last edited by Hero; Dec 26th 2015 at 04:19 AM.
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Old Dec 26th 2015, 06:42 AM   #4
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Classification of Waves

Haallo again, Hero.

Let us consider just one of your queres namely " isn't propagation the same tjhing aas trtavelling? (or something of thst sort).

No. Most definitely not. Propaagation does not mean lateral translation but is more akin to extending.

A root extending out from a plant by both chemical action and force is not propagating. True ity may be that a Light wave may appear to be travelling but, lacking a medium or a process, it does not achieve anything tangible.

You could say however that it moves information - but now I am called upon to define the term "information"?

Of itself it does not even "move" information. It is not until a Light-wave is detected (and absorbed/ destroyed) by our sensory apparatus that information enters the picture.?

Information propagates as a sound-wave through air by means of a series of travelling pressure-fronts which, in passing. act mechanically on our ear-drums;' from then on it's an electrical process. These pressure fronts are created by particles of air moving backward then forward along the direction of propagation. Hence longitudinal vibrations - in the process they don't get anywhere but are just "marking time".

Waves travelling across a water-surface (driven by wind) are similarly an illusion. Here the water particles are moving upward and then downward across the direction of propagation (said to be moving orthogonally) . Watch anything that is floating on that surface and you will see that it moves only vertically ?

Because the mechanical movement is across the direction of "travel" such a wave is described as transverse.

As a matter of interest a pressure microphone responds to the pressure fronts bexause they mechanically distort a diaphragm.

By contrast a velocity microphone has a lightweight ribbon wich is carried forward and then backward by the moving particles of air and its output is proportional to the SPEED at which tthe particles are moving.

Ken
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Old Dec 26th 2015, 10:03 AM   #5
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Mr Green, you have now sullied the water as well as "dirtied the windscreen".

I will work through what you have written and get back you to. Thank you.
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Old Dec 28th 2015, 02:33 PM   #6
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Hello Hero,
To pick up your original goal of classification of waves, I think you need to widen your scope .

Firstlly it is important to establish what you mean by a wave and what is the difference between a wave a single event a vibration or oscillation.

The second point is to identify the players on the wave stage.
There are several and each has a particular part to play and it is these parts that determine wave type.

Oh, yes wave type.

Well I can think of
progressive or travelling
stationary or standing
solitary or soliton

(solitons are particularly important in modern optics)

Then there is the mode of vibration

Transverse
Longitudinal
Torsional
Orbital
Surface
Combined

Waves can be

One dimensional
Two
Three dimensional
Plane
Circular
Spherical

Some other properties used to characterise waves are

Polarisation
Simple or fundamental
Compound
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Old Dec 30th 2015, 07:03 AM   #7
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Electromagnetic Medium.

Note that this just a thought I have had,
I put it out there to be shot at (and probably shot down).

The vacuum is not nothing.

The electromagnetic field at a point in space is in balance,
an electromagnetic disturbance upsets this balance creating a restorative tension.
Pushing a balanced system out of balance and the restorative tension thus created is the basis of all waves.
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Old Dec 31st 2015, 01:22 AM   #8
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Originally Posted by Hero
I can't paste to flowchart on this forum ...
Why not? All you need to do is use a screen capture which takes a snapshot of your screen and makes an image out of it and in the end places it into an image file. I myself have done this perhaps over a thousand times when I was working on my physics website. It was the only way that I knew how to place equations in an HTML file.

Originally Posted by Hero
Please can someone look at them and correct me if there are errors or add information where it is lacking.
Sure.

Originally Posted by Hero
Waves - longitudinal or transverse.

Transverse waves - mechanical transverse or electromagnetic transverse.

Mechanical transverse waves - surface water waves, wave on a rope, seismic S waves.
What's your reasoning for asserting that all transverse waves are mechanical in nature? Although Wikipedia agrees with you I'm questioning Wikipedia in this instance. Normally their almost always correct. A wave can be comprised of energy of even temperature, neither of which are necessarily mechanical. Right now I have in mind heat moving along a glass rod. The wave function in quantum mechanics is neither longitudinal nor transverse and requires no medium at all. Please keep that in mind.

For purposes of your interest in the subject we'll skip that and assume that the Wikipedia entry at: https://en.wikipedia.org/wiki/Wave is exactly correct. Okay?

Originally Posted by Hero

Electromagnetic transverse waves are visible light, gamma rays, radio waves.

Mechanical transverse waves require a medium for propagation (travel).

Electromagnetic transverse waves do not require a medium for propagation and can travel in a vacuum but also through a medium.

Longitudinal waves sound waves, seismic P waves, underwater waves

Longitudinal waves - require a medium
That seems correct to me.
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Old Jan 25th 2016, 03:28 AM   #9
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Thanks PMB. I've been without a computer for a while and just got back onto forum today
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