# Polarized Light

1. Sep 28, 2004

### xenogizmo

Hey guys,
I was just wondering, why can some pictures be only seen through a polarizing film, or when illuminated by polarized light? I would really appreciate your answer.
Thx,
Xen0

2. Sep 28, 2004

### Gonzolo

Do you mean 3D movies, where they give you red and blue, polarized goggles?

3. Sep 28, 2004

### xenogizmo

No, not really..
It's like a picture, if you look at it with the naked eye, you see nothing, but if you shine polarized light on it you see the picture.. What's the explanation of this?

4. Sep 28, 2004

### Vern

I think you mean holography. I've studied it but don't really understand just exactly how it works. The effect gives an image that seems to occupy real 3-D space.

5. Sep 28, 2004

### xenogizmo

hey guys I think I might have said the question in a wrong way or something.. the phenomenon i'm talking about is not 3D..
It's just a 2D picture, only difference than any normal picture is that it ONLY appears under polarized light.. Helpful?

6. Sep 28, 2004

### Gonzolo

Where did you see this? (I think I can explain it but want to be sure I got all the givens...)

7. Sep 28, 2004

### xenogizmo

In the chemistry lab, the demonstrator had a black picture, that showed a different picture under normal light and polarized light

8. Sep 28, 2004

### Gonzolo

Well, I'll admit I have never seen this, but here is what I can say.

Polarization basics:

Chemical polarizers are made of long molecules, like the bars of a jail cell, say along the y-axis. Polarized light on the other hand is made of an E-field (electric field) that oscillates in one direction (y or x) perpendicular to the direction of the light beam (z). (We can practically always ignore the corresponding magnetic field in (x) when speaking of polarization.) Regular light has an oscillating E-field in both (y) and (x).

If y-polarized light hits y-polarized molecule (jail door), it can be totally absorbed, or reflected. The conducting electrons will run along the long molecules and either absorb or reflect the light.

On the other hand, x-polarized light will go through y-polarized molecule, since the conduction electrons can't follow such E-fields.

Regular light will be half transmitted, half absorbed + reflected.