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Old Feb 26th 2014, 11:38 AM   #1
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Question Some beginner questions about sun rays, magnetism and electro-magnetism.

Hello, I'm new to this forum, and I wonder if anyone will answer my questions.
My questions are:
1: What is a sun ray ? What is it made of?
2: What is magnetism? How does it work?
3: What is electro-magnetism, and how does it work?

I will be grateful for answers. Thanks a lot !

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Old Feb 27th 2014, 10:23 AM   #2
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Lots of analogies!

A "sun ray" is an example of electromagnetic radiation.
Electromagnetism is the term used to describe one of the observed interactions between subatomic particles.
Electromagnetic radiation transfers energy between subatomic particles.

A simplified way of visualising might be that there is a balance between magnetism and electricity,
If that balance is disturbed there is a tension created toward restoring the balance.
Rather like a plucked string the energy then swings back and forth between electricity and magnetism.
The key point is that this disturbance doesn't just stay where it is, it travels.

However, this is a description by analogy,
as one tries to pin down the description more precisely it becomes rather more slippery.

When it really comes to the crunch, the true answer is I don't know!

Last edited by MBW; Mar 2nd 2014 at 06:24 AM.
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Old Feb 27th 2014, 04:10 PM   #3
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Question

A "sun ray" is an example of electromagnetic radiation.Electromagnetism is the term used to describe one of the observed interactions between subatomic particles.
Electromagnetic radiation transfers energy between subatomic particles.

Ok, then I have some more questions: What interactions between subatomic particles does Electromagnetism consist of?
What is Energy?

Electricity is the transference of electrons betweem atoms, right? So what do you mean by "balance between magnetism and electricity,
If that balance is disturbed there is a tension created toward restoring the balance." ?

Thanks a lot
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Old Mar 2nd 2014, 08:10 AM   #4
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Why has a long tale

It is often surprising how little one has to dig to find the limits of human understanding (particularly this human)!

What is Energy?
Most replies to this question relate to what Energy does, rather than what energy is.
I have my own ideas, which I must warn might not be agreed with by main-stream physicists.
An exchange of energy is in essence an exchange of probability.
The arrangement after an energy exchange will be more probable than the arrangement before.
Consider a pencil balanced on its base, it is possible, but a bit improbable,
the slightest knock will cause it to transfer energy to reach the more probable situation of lying flat on the table.

Back to electromagnetism (and a major problem here is My lack of understanding).
Subatomic particles have various properties, for example, position, momentum, charge and spin.

An electromagnetic wave is created when the momentum of a charged particle changes.
For example light waves are created when an electron changes its momentum with respect to the nucleus of the atom.
Radio waves are created (for example) when electrons race up and down the aerial of the radio transmitter.

Spin is something I admit I don't understand,
It is not directly analogous to what one would recognise in the macroscopic world as spin and it is related to magnetism.
That is about my limit, perhaps someone else out there can elaborate.
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Old Mar 2nd 2014, 11:11 AM   #5
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MBW: thanks for the answer. I got some more questions from your post now that I hope you'll try to answer. So a light wave is an electromagnetic wave which is created when the momentum of a charged particle changes. When an electron changes its momentum with respect to the nucleus of the atom. What is the momentum of a charged particle ? What does it mean that a particle is charged?

Thanks
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Old Mar 3rd 2014, 05:24 AM   #6
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What also has a long tale

Momentum is the product of Mass and Velocity
(Velocity being a combination of speed and direction)
What is Mass & What is Charge? What is Distance and What is Time?
At this fundemental level, I don't know!

All I can say is that:
Fundemental particles must exhibit different properties, otherwise everything would be exactly the same.
Everything being exactly the same means no change is possible, indeed I would say it is equivalent to nothing at all.
Why the fundemental particles adopt the particular ways of having different properties that we observe (in this universe) is an interesting question.
The leading contender for an answer to that question is that there are lots of universes.
Each universe has it's own different way of organising the fundemental properties.
Thus ours is just pure chance.
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Old Mar 5th 2014, 10:45 AM   #7
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So a light wave is an electromagnetic wave which is created when the momentum of a charged particle changes. What decides the wavelength of the sun-ray? Can you explain any closer how a light wave comes to be? The momentum of a charged particle changes in what way? You said when an electron changes its momentum with respect to the nucleus of the atom.

Thanks
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Old Mar 6th 2014, 10:48 AM   #8
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Exclamation Warning You are Approaching the Edge of My Knowledge!

Momentum is a composite property based on the mass, and velocity
Velocity is a composite property based on the speed and direction.

A change in velocity is an acceleration (either a change in speed or a change in direction).
Thus a change in momentum implies a change in mass or an acceleration (or both)
[Note, for a mathematician, a deceleration is just a negative acceleration].

For electrons rushing up and down an aerial, the change in momentum is (I think) obvious.
For electrons in an atom, the change is more subtle (and more complex).
The negatively charged electrons in a atom maintain a balance with the positively charged protons in the atom, based on their relative charge and momentum.
The charge is constant, but the momentum can change.
When an electron emits a photon of light it looses energy and thus (via E=mc˛) it also loses mass.
Note that this means it changes momentum.

A photon is a single tiny packet of electro-magnetic radiation, a light ray is made of lots of photons.

I'm starting to struggle here, anyone else out there what to have a go?
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Old Mar 6th 2014, 11:57 AM   #9
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For electrons rushing up and down an aerial, the change in momentum is (I think) obvious. Why is the change in momentum so obvious for electrons rushing up and down an aerial, do you mean it stops and accelerates again every time it goes up and down? And that makes the electrons momentum change, and it emits fotons? Can one use up the electrons then, because they lose mass? Are all electromagnetic waves made out of fotons? Can you explain why the atoms in the sun emits fotons ?
And do you mean that a change in velocity is an acceleration of the speed of the spin and not the hole electron? A change in momentum implies a change in mass or an acceleration. Acceleration of the hole electron is what you mean ?

Thanks
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Old Mar 10th 2014, 10:06 AM   #10
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The motion of electrons in an aerial is caused by the radio transmitter applying a varying voltage from one end of the aerial to the other,
When the voltage is applied in one direction the electrons move one way,
when the voltage is reversed, the electrons move the other way.
So Yes, the momentum change is where the electrons decelerate in one direction, then accelerate in the other direction.

An electron has a "ground" state which is it's minimum energy/mass
{Note that energy and mass can, in a very direct sense, be considered alternative names for the same underlying property}.
An electron can gain energy over and above it's ground state (by absorbing a photon)
Having absorbed a photon, it can, at some later time, re-emit the photon.

The sun generates vast numbers of photons in its core via nuclear fusion.

These photons are absorbed by the electrons in neighboring atoms.
Then these electrons re-emit the photon, which is re-absorbed by the next atom.

The photon is thus passed, from atom to atom, until it reaces the surface of the sun.
Finally, it is passed from an atom at the surface of the sun to an atom in your eye.
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