# Electromagnetic polarisation

Discussion in 'General Electronics Chat' started by mentaaal, Sep 15, 2007.

1. ### mentaaal Thread Starter Senior Member

Oct 17, 2005
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0
HI guys, ok i have started college and have a pretty scatty physics teacher...
He was demonstrating for us how a structure of parallel metal bars can polarise microwaves. What i was trying to ask him is, if the metal bars can stop the electric aspect of the waves, how do they not stop the magnetic aspect? I mean the magnetic field is dynamic in nature, surely this would induce a current in the metal and just short it out?

Thanks for the help guys!

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
All you need is a series of parallel lines to polarize light. At least, that's how the people at Polaroid do it. It's not significant to make a conducting path for current - remember that polarizers just eliminate that portion of the light with an amplitude at right angles to the plane of the polarizing structure.

Photons are very easy to stop.

3. ### mentaaal Thread Starter Senior Member

Oct 17, 2005
451
0
Thanks for the reply but i am still confused...
I am led to believe that light is an electromagnetic wave which has an electric field in one plane and has a magnetic field perpendicular to it. I was trying to ask my teacher why is it that the parallel metal bars stop the electric field from passing through it ( this means that the electric field is only allowed to travel in a plane parallel to the bars which is what polarises the wave in general by stopping the electric field from passing through the metal bars) but allows the magnetic field to pass through it?

If you can imagine the electric field propagating in a plane parallel to the grid, surely the magnetic field will still pass through the metal bars, and for this to occur the metal bars have to be allowing the magnetic field aspect of the wave to pass unhindered, the question i am asking is how is this possible when a changing magnetic field across a conductor induced current in the conductor? Or is this because of the way that the polariser is orientated in relation to the wave?
Like if the wave were passing the grid like a person would walk over a cattle grid, would that orientation cause a voltage to be impressed across the ends of the metal bars?