# Linear polarized light and polarisation

hi

if you have linear polarized light and you have a metal grid and the angle between the e-vector and the metal grid is 30°. now you split up the e-vector in one component parallel and one component perpendicular to the metal grid. okay. so the component of the wave, that survives this prodcedure is the component perpendicular to the metal grid that has an angle of 90°-30°=60° to the initial wave. ( in the opposite direction)

my problem is: that if you now have another grid, that has a component that is parallel to the initial wave, this original wave would have not been able to pass the grid. but, if you regard the wave with the shift of 60°. there is a component perpendicular to the initial wave that could also pass this grid.

my only question is: are these considerations all right so far? cause i am a little bit wondered about this fact...

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Born2bwire
Gold Member
You don't really have a component that is perpendicular to the grid though unless you are talking about one that is normal to the grid's plane. There are two modes, transverse magnetic and transverse electric, to the grid's plane. So in the TM mode, the electric field must lie in the plane of the grid and so you can always decompose the electric field into two components that point along the two axes of the grid.

In the TE mode, the electric field has a component that lies in the plane of the grid (which we know will be cancelled out via above) and one that lies perpendicular to the grid. But if the normal component would to pass through, then this means that the transmitted radiation could only travel along the metal grid (because in an open isotropic medium EM waves are transverse to the direction of propagation). So now, if it could exist (which it doesn't, well in general it doesn't) you can only have a transmitted surface wave.

So either way, you cannot have transmission of the electromagnetic wave through a grid provided that the grid is dense enough and has a high enough conductivity to extinguish the wave.

EDIT: Are you talking about a grid or a grating?

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hi

if you have linear polarized light and you have a metal grid and the angle between the e-vector and the metal grid is 30°. now you split up the e-vector in one component parallel and one component perpendicular to the metal grid. okay. so the component of the wave, that survives this prodcedure is the component perpendicular to the metal grid that has an angle of 90°-30°=60° to the initial wave. ( in the opposite direction)

my problem is: that if you now have another grid, that has a component that is parallel to the initial wave, this original wave would have not been able to pass the grid. but, if you regard the wave with the shift of 60°. there is a component perpendicular to the initial wave that could also pass this grid.

my only question is: are these considerations all right so far? cause i am a little bit wondered about this fact...
It's all correct. Each polarizer launches a new wave which is how multiple polarizers can rotate the original polarization by 90 degrees.

It's all correct. Each polarizer launches a new wave which is how multiple polarizers can rotate the original polarization by 90 degrees.
thank you that was exactly what i wanted to know...