How to build a simple polarization filter

[elou]

TL;DR

This filter will not necessarily function exactly as a polarization filter, but will maybe help visualize some aspects of it. Also, to keep things simple, I will be using "filters" with a single slit.

For that we will need a laser pen and two square pieces of opaque, non reflecting material. In both these squares a slit will be cut, wide enough to let a beam of the laser pass through without any refraction effects.

First, after the laser has been turned on, one of the squares is placed in front of the beam, allowing free passage to the light.
If I am right, I did not try it, the spot on the screen will become smaller and smaller if the square is rotated to the left or to the the right until it is in a horizontal position. More light will come through if the square keeps being rotated until it has reached a vertical orientation again.

Then, the second square, placed in front of the first one, farther from the laser, is also slowly rotated left or right. Depending one the starting orientation, more or less light will pass, to the point that an orthogonal orientation of the second square relative to the first one will achieve an almost total extinguishing of the light passing through.

 

[sophiecentaur]

TL;DR Summary: This filter will not necessarily function exactly as a polarization filter, but will maybe help visualize some aspects of it. Also, to keep things simple, I will be using "filters" with a single slit.

If I am right, I did not try it,

Your description of your proposed method is confusing but it seems that you don't know what polarisation of EM waves means. But -"try it" and see if you are right. (Hint. You are not) And you don't need a laser for any of this.

Then read about EM wave polarisation and polarisers. A simple search will imply that you need polarising material and that's not stuff that you can make, yourself. This is a great example of how Google Searches can get in the way of learning basics; I looked at page after page before I found anything that talked about basic polarisers (there's no money in basic optics).

You will need to know about Brewster's Angle and how it can be used to polarise light. In the early days (when you couldn't buy polarisers) this was the only way to produce polarised light.

PS your idea about using slots has applications for much longer wavelengths, such as microwaves. Not for light though.

PPS Two clean sheets of good glass can show the effects of polarisation - all on the kitchen table.

 

[elou]

PS your idea about using slots has applications for much longer wavelengths, such as microwaves. Not for light though.

Do you think that the light that would get through would not get dimmer by rotating the squares appropriately?
For the rest I agree that my set up is a far cry from what is meant by polarization.

 

[sophiecentaur]

Do you think that the light that would get through would not get dimmer by rotating the squares appropriately?

Two clean sheets of good glass can show the effects of polarisation - all on the kitchen table. Not a high degree of polarisation but you can see a change in brightness - as with polaroid sunglasses.

 

[sophiecentaur]

I misunderstood. your last post - it's nonsense. The results wouldn't in any way be affected by polarisation. If you're not prepared to read up on this, you are wasting your time (as in that other thread).
Don't bother to reply until you have done some independent reading.

 

[elou]

Two clean sheets of good glass can show the effects of polarisation - all on the kitchen table. Not a high degree of polarisation but you can see a change in brightness - as with polaroid sunglasses.

I'll take that as a yes. My disclaimer stands. This is not a replacement for polarizing filters, so the title might be too ambitious.

I was wondering what the effect would be if we made the slits, smaller and more numerous..
I also wonder what happens when two diffraction gratings are rotated relative to each other.

 

[sophiecentaur]

so the title might be too ambitious.

The word is not "ambitious"; it's "nonsense". Argue with the text books - don't argue with me because you cannot conceive that you could be wrong.

 

[elou]

The word is not "ambitious"; it's "nonsense". Argue with the text books - don't argue with me because you cannot conceive that you could be wrong.

How about we stop talking about polarization? What I am proposing is as real as anything else. I am not claiming any particular interpretation. Only wondering what the result will be when light has to go through a combination of slits. How is that nonsense?

 

[A.T.]

I did not try it

Why not?

 

[elou]

Why not?

I will, in time.

 

[Vanadium 50]

IBTL.
What is the utility of a parade of incorrect statements here?

 

[Doc Al]

I did not try it

That's a good note on which to close this thread.