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Old 06-25-2017, 03:40 AM
 
21 posts, read 12,329 times
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I have always found the physical nature of electromagnetic waves to be fairly confusing, and I am not sure how to imagine them.
It is easy to understand mechanical waves such as water waves and pressure waves, since they are really just energy that travels in a medium and causes displacements etc - and they have actual physical wave shapes - but how do electromagnetic waves work?
For example, what happens to light when I shine it through a polarizer?
My first gut reaction was that light would take the form of the polarizing axis, but I immediately realised that this wasn't true, since light isn't affected by geometry like that.
I know that the polarizer "filters out" the components that are perpendicular to the axis, but what does this mean in the real world more than a reduced intensity?
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Old 06-25-2017, 09:19 PM
 
Location: Westwood, MA
2,900 posts, read 3,733,226 times
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To really understand classical EM waves you need to know a little bit about electricity and magnetism, specifically Maxwell's equations.

To really understand them takes the better part a semester course (and that's just to a basic level), but I'll try the three minute version:

Charged particles create an electric field that causes a force on other charged particles. Changing electric fields create a magnetic field. Magnetic fields produce a force on moving charged particles. Changing magnetic fields produce electric fields.

Since changing electric fields produce magnetic fields and changing magnetic fields produce electric fields, it's possible to produce a self-sustaining wave of changing electric and magnetic fields without any electric charges nearby. The electric fields changes in such a way that it produces a changing magnetic field that in turn produces a changing electric field and on and on at the speed of light.

These fields are produced at right angles to each other and the direction of propagation. The polarization direction of the electric field. A polarizer has a conductor parallel to one of the directions and not the other. Light polarized along that direction will be absorbed and light polarized along the other direction will be transmitted.
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Old 07-24-2017, 03:25 PM
 
Location: Londonderry, NH
41,043 posts, read 45,624,979 times
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After figuring out Maxwell's Equations the OP should study multiphase electricity.


There is no simple way to understand electromagnetic waves.
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Old 08-09-2017, 03:47 AM
 
1 posts, read 196 times
Reputation: 10
Quote:
Originally Posted by Markus86 View Post
I have always found the physical nature of electromagnetic waves to be fairly confusing, and I am not sure how to imagine them.
It is easy to understand mechanical waves such as water waves and pressure waves, since they are really just energy that travels in a medium and causes displacements etc - and they have actual physical wave shapes - but how do electromagnetic waves work?
For example, what happens to light when I shine it through a polarizer?
My first gut reaction was that light would take the form of the polarizing axis, but I immediately realised that this wasn't true, since light isn't affected by geometry like that.
I know that the polarizer "filters out" the components that are perpendicular to the axis, but what does this mean in the real world more than a reduced intensity?
You have remember that all we can do is use analogies in order to describe this kind of phenomena. We use the term 'waves' to describe electromagnetic radiation but the only way we have to detect stuff is to measure it, which means we use what tools we can to do it. Then the maths kicks in to model it and pattern it and then analogies such as 'wavelike' are used as a shorthand in describing it to aid understanding. But there is no reason you should not imagine waves to represent EM radiation because this is something human beings can do based on how their brains work. In the final analysis, any scientific knowledge is an interpretation which seems to work based on consistency, which is useful.
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