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Author Topic: How can scientists learn the shape of electromagnetic waves?  (Read 4642 times)

Offline thedoc

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Nadia Adam  asked the Naked Scientists:
   Hello  thanks for responding to my last question.
I have another question  how do scientists know the shape of electromagnetic  waves .Thanks

   

What do you think?
« Last Edit: 19/10/2015 11:50:01 by _system »


 

Offline PmbPhy

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Quote from: Nadia Adam
Hello  thanks for responding to my last question.
I have another question  how do scientists know the shape of electromagnetic  waves .Thanks
They use what's known as Maxwell's Equations (ME). The solutions of ME are vectors of both the electric and magnetic fields. Those are the only quantities (at least the best quantities) that can be given meaning to the question "the shape of electromagnetic waves?"
 

Offline Colin2B

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how do scientists know the shape of electromagnetic  waves
The electric field can also be measured, for example with radio waves it is possible to use antenna to measure the electric field at different points in space and in different orientations so building up a picture of the wave.

 

Offline evan_au

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There are also software packages that allow simulation of electric and magnetic fields in various environments. These may be used to analyze and design circuits at optical or radio frequencies.

In this example, microwaves do a right-angle bend in a curved waveguide. (Other software packages are available!)
 

Offline Thebox

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I thought we define the shape by measuring device and it is timing of a wave rather than a shape?

Shape is something we define , patterns are something we establish,timing is something we measure?
 

Offline Colin2B

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I thought we define the shape by measuring device and it is timing of a wave rather than a shape?

Shape is something we define , patterns are something we establish,timing is something we measure?
If you look at waves coming in to shore they have a shape shown by a varying height. We can measure how that shape varies with time. We can also measure their frequency by timing how long it takes the peaks (or any other point) to pass by.
Think AC voltage, it's intensity (height) varies with time.
 

Offline Thebox

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If you look at waves coming in to shore they have a shape shown by a varying height. We can measure how that shape varies with time. We can also measure their frequency by timing how long it takes the peaks (or any other point) to pass by.
Think AC voltage, it's intensity (height) varies with time.

I would not disagree, but shape is something we define by the displacement of atoms in a volume of space, where as frequency, a rate, is measured by distance between the peak flows which is defined by the process rather than us. When we observe waves at the beach we observe the shape and define the shape calling it a wave, but the spacing of waves is defined by the natural events and not defined by us?

 

Offline Colin2B

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[.. When we observe waves at the beach we observe the shape and define the shape calling it a wave, but the spacing of waves is defined by the natural events and not defined by us?
So are you saying that the height of the waves and its variation with time is not a natural event?
 

Offline Thebox

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[.. When we observe waves at the beach we observe the shape and define the shape calling it a wave, but the spacing of waves is defined by the natural events and not defined by us?
So are you saying that the height of the waves and its variation with time is not a natural event?
No not at all, height of the waves if force related, its variation is a variation of force, the displacement of the water, is defined by this, we call it a wave and define the shape as a wave like we define a circle a circle. We measure a rate by a distance, an x-axis if you like.   But to consider water and waves of water being a comparison to something without physical body, in my opinion is not really good.
My problem is this, you measure light by the troths etc and a distance between them, by using device, a screen you view etc, oscilloscope I think it is called, but this is not natural.   
I just think anything to do with light, science is making the measurement rather than the measurement being natural. I think observer effect is what a wave is.

Like the slit experiment, ''light does not naturally pass through slits'', science makes the angled slit to change the light and create an interference pattern, the natural of light in space does not behave that way.

Why does light act like a wave and a particle, because science makes it happen. There is nothing to measure until somebody measures it. We also know the cat in the box is really dead because we can calculate the volume of air in the box and how long the cat has to live before it suffocates, and also the atomic decay of the cat is not considered so the gas is released either way.




« Last Edit: 20/10/2015 11:39:54 by Thebox »
 

Offline Colin2B

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....to change the light and create an interference pattern, the natural of light in space does not behave that way.
Actually it does, it just happens so quickly and is constantly moving that we can't usually see it, the slit and other experiments provides a stationary pattern that we can see. Sometimes we can see the stationary effects around the edges of clouds and in fog, also in oil on a puddle, so it does happen away from the slits.
We also see the same effects with radio waves, water waves and sound waves. They are there whether you choose to believe or not.
 

Offline Thebox

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....to change the light and create an interference pattern, the natural of light in space does not behave that way.
Actually it does, it just happens so quickly and is constantly moving that we can't usually see it, the slit and other experiments provides a stationary pattern that we can see. Sometimes we can see the stationary effects around the edges of clouds and in fog, also in oil on a puddle, so it does happen away from the slits.
We also see the same effects with radio waves, water waves and sound waves. They are there whether you choose to believe or not.

I have not said that I do not believe waves exist, I said I believe science makes waves by device .   Also you know I do not think waves exist of space, we know sea waves are made by force, so can we conclude a force is needed to create a wave?

If you accept the sea to be wavelike and light waves a comparison, then surely the comparison also needs a force applied to make a wave?


How can something be a wave without any acting forces? 



 

Offline Colin2B

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I have not said that I do not believe waves exist, I said I believe science makes waves by device .
I'm not going to ask about this because it sounds like a new theory.
What I will say is that science describes waves, their properties and their behaviour.

can we conclude a force is needed to create a wave?
A movement can create a wave. A transfer of energy can create a movement.
An electron moving can create a light wave.
« Last Edit: 21/10/2015 08:52:36 by Colin2B »
 

Offline jeffreyH

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Light moves at a constant speed. It may vary on a coordinate basis as viewed by remote observers but in any local frame light will be measured to have exactly the same speed everywhere. A gravitational field will slow the light and induce time dilation proportionally to every other particle in the same frame of reference. The most interesting part is what exactly does gravity do to change the wavelength? Another very interesting question is what do varying sizes of particle mass do to the wavelength of the said particle?
 

Offline Thebox

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Light moves at a constant speed. It may vary on a coordinate basis as viewed by remote observers but in any local frame light will be measured to have exactly the same speed everywhere. A gravitational field will slow the light and induce time dilation proportionally to every other particle in the same frame of reference. The most interesting part is what exactly does gravity do to change the wavelength? Another very interesting question is what do varying sizes of particle mass do to the wavelength of the said particle?


Light only propagates at a constant speed through ''emptiness'', the speed of light when interaction is involved from an invert force is not the same constant speed as light propagating through ''emptiness'.  Light slows down in a medium, so if you lived under water, light is not a constant compared to above the water, C is only constant in a vacuum.
Gravity is a constant, the force of gravity is a constant rate on the mass being pulled while the mass is in a ''stationary'' initial reference frame, the mass is always accelerating inwards, outwards force/momentum p, de-accelerates the gravity flow.

g=p(0)

+E=+F=W=-g=+p?


Answer to the thread title - by considering EMR to be an isotropic ripple rather than a wave.

« Last Edit: 21/10/2015 10:05:13 by Thebox »
 

Offline Colin2B

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Answer to the thread title - by considering EMR to be an isotropic ripple rather than a wave.
A ripple is a wave.
But maybe you are starting to understand something.
 

Offline Thebox

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Answer to the thread title - by considering EMR to be an isotropic ripple rather than a wave.
A ripple is a wave.
But maybe you are starting to understand something.

No a wave travels a linearity like a surface ripple, an isotropic ripple is different.  A wave of sea flattens out when it crashes.
 
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Offline Colin2B

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... an isotropic ripple is different...
Not from what I've seen.
Or you are not explaining what you mean
 

Offline Thebox

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... an isotropic ripple is different...
Not from what I've seen.
Or you are not explaining what you mean

I am in main so must be careful not to stray.   Imagine a sphere, then expand this sphere the smallest amount available, lets say for example 0.0000000001mm.

However the sphere is not really expanded, the 0.0000000001mm. is a convertual isotropic layer.  The next layer is emitted and so on.

 

Offline Colin2B

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I am in main so must be careful not to stray.   Imagine a sphere, then expand this sphere the smallest amount available, lets say for example 0.0000000001mm.

However the sphere is not really expanded, the 0.0000000001mm. is a convertual isotropic layer.  The next layer is emitted and so on.
definatly new theory, makes no explanation relevant to topic.
Let's leave it at that, you don't understand me, I don't understand you.
 

Offline Thebox

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I am in main so must be careful not to stray.   Imagine a sphere, then expand this sphere the smallest amount available, lets say for example 0.0000000001mm.

However the sphere is not really expanded, the 0.0000000001mm. is a convertual isotropic layer.  The next layer is emitted and so on.
definatly new theory, makes no explanation relevant to topic.
Let's leave it at that, you don't understand me, I don't understand you.

Well its not really a new theory it is what we already know about light emitted from a sphere. It is equal in all directions (isotropic) , there is seemingly an even distribution from a surface according to surface structure, light fills all the gaps between a light source and an object in the lights path, there is no gaps in the white light/clear light of space. The emittance speed is constant of a light source, so all ''virtual particles'' travel in unison in lines/layers.
I agree we do not understand each other, but what I explain is never a new theory, it is present information perceived differently.
All my perceived ideas are , science told me this is what happens in so many words.

added - a wavelength is 2d?

« Last Edit: 21/10/2015 19:49:46 by Thebox »
 

Offline Colin2B

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..it is present information perceived differently.
but often incorrectly, as here. But you are getting some bits right.
However, if you want to discuss this you will have to open a topic in Chat or Can't be true, because however you try to say it, a ripple is a wave.

added - a wavelength is 2d?
1d, there is only length
« Last Edit: 21/10/2015 23:47:43 by Colin2B »
 

Offline Thebox

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1d, there is only length

But light is multi-dimensional?
 

Offline Colin2B

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I will answer this because it is relevant to the topic
1d, there is only length
But light is multi-dimensional?
You specifically asked about its wavelength which has a single dimension, length.
Other dimensions would include intensity (a function of amplitude - equivalent to wave height in water) and polarisation.
The question in topic header is about EM waves in general, with radio waves you can describe the frequency components and phase relationships of a modulated wave - which defines the wave shape. You can also do this for light, but it is easier to understand if you start with radio.
The shapes of other types of wave eg sound and water waves can be described in the same way.

I will take a moment to explain why I will answer questions related to this topic but not those I consider to be off topic and new theories.
Let's take the example of a ripple. A ripple is a small wave by definition so to say light is not a wave but isotopic ripples is a new theory.
Similarly to say light does not naturally pass through slits, to talk of virtual particles, to say it does not exist of space, all of these and more are not recognised light theory. If you want to discuss these then start a different topic in another 'lighter' area otherwise your replies need to stick tightly to the topic and recognised, eg Wiki, theory. If you don't, mods will delete your posts or parts of them. And I will not answer them.
 

Offline Thebox

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I will answer this because it is relevant to the topic
1d, there is only length
But light is multi-dimensional?
You specifically asked about its wavelength which has a single dimension, length.
Other dimensions would include intensity (a function of amplitude - equivalent to wave height in water) and polarisation.
The question in topic header is about EM waves in general, with radio waves you can describe the frequency components and phase relationships of a modulated wave - which defines the wave shape. You can also do this for light, but it is easier to understand if you start with radio.
The shapes of other types of wave eg sound and water waves can be described in the same way.

I will take a moment to explain why I will answer questions related to this topic but not those I consider to be off topic and new theories.
Let's take the example of a ripple. A ripple is a small wave by definition so to say light is not a wave but isotopic ripples is a new theory.
Similarly to say light does not naturally pass through slits, to talk of virtual particles, to say it does not exist of space, all of these and more are not recognised light theory. If you want to discuss these then start a different topic in another 'lighter' area otherwise your replies need to stick tightly to the topic and recognised, eg Wiki, theory. If you don't, mods will delete your posts or parts of them. And I will not answer them.


The topic says how can science learn the shape of electromagnetism?  to learn something it needs to be understood, if you don't understand it, then how can you learn something about it?
It is no good saying a ripple or a wave represents a sphere output when a sphere is a 3d output and you only measure a 1d version.



I am not straying off topic Colin, I am helping science to understand the ''shape'' of electromagnetic waves by discussing it.   An isotropic ripple is not new, science says light is released in all directions from the sun, you say a ripple is a wave, therefore you are saying it is an equal in all directions ripple, I miss your point Colin, this is not off topic just thinking different about shapes.


''With radio waves you can describe the frequency components and phase relationships of a modulated wave''


science makes the wave by device, the wave is not real in my opinion so has no shape.
Like the sea has no waves if there is no wind,

so why would light wave if there is no ''wind''?
 
« Last Edit: 22/10/2015 12:57:25 by Thebox »
 

Offline jeffreyH

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You can also think of a wave as a varying intensity. If you were to set up a laser and have an automatic adjustment on how many photons were released at any time this could vary the light intensity in a set wavelike pattern. It is like turning a torch on and off except rather than a sudden interruption of the light it varies up and down. An ensemble of particles can thus be thought of as describing a wave. As energy varies in a system the area under the curve of the function determining the energy fluctuations can also be wavelike.
 

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