Insights Blog
-- Browse All Articles --
Physics Articles
Physics Tutorials
Physics Guides
Physics FAQ
Math Articles
Math Tutorials
Math Guides
Math FAQ
Education Articles
Education Guides
Bio/Chem Articles
Technology Guides
Computer Science Tutorials
Forums
Trending
Featured Threads
Log in
Register
What's new
Search
Search
Search titles only
By:
Menu
Log in
Register
Navigation
More options
Contact us
Close Menu
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Forums
Physics
Classical Physics
Optics
Trying to Understand the Polarization of light
Reply to thread
Message
[QUOTE="Merlin3189, post: 6840683, member: 542077"] Glad to see this video helped a bit. I think it is brilliant and really helped me a lot. What I think may be hanging you up now, is that a vector can always be replaced by a pair of orthogonal vectors, which totally represent it and can in turn be replaced by a single vector (their sum), which, if nothing has been done to them meanwhile, will be an exact recreation of the original vector. [That of course (IMO) is mathematical sophistry! The two component vectors never existed - any more than the original vector did! Vectors are just a mathematical way of describing light: and both descriptions, as a single vector and as a pair of vectors, are equally valid. That (personal view) aside, let's look at the light and how it behaves. ] 12:50 on, shows how light can have its polarisation changed by a linear polariser. A linear polariser passes all light parallel to its polarisation, and blocks all light perpendicular to its polarisation What about light at other angles? It treats it as if it were two waves, one parallel and one perpendicular to its polarisation. Then it blocks the one and passes the other, giving you linearly polarised light with a different polarisation from the incoming wave. Just as if it were doing the maths and resolving the incoming vector into two orthogonal vectors. I think your question is, not the maths, but why the polariser behaves like this. If you look at the light coming out of each polariser, it is always plane polarised in the preferred direction. (This is shown in the video by the stripes, which run in the blocking direction.) Now I don't know exactly how this works (you'll have to find a quantum physicist for that), but I'll give you my classical semi-understanding. Light interacts with matter, causing it to slow down, be reflected, refracted and polarised, because it excites electrons. This excitation may depend on the relative orientation of molecules and the electric field of the light. OTOH the re-emitted light depends only on the orientation of the molecules. In a polarising material, the significant molecules are all or mainly aligned in one direction. That, of course, is the arm-waving you mention! And some people describe it as absorption in one direction. I can't see how you can get away without both absorption and emission: both can be achieved by exciting electrons, but I personally can't get the numbers to work when both happen. You may be interested to watch [URL='https://www.youtube.com/watch?v=KM2TkM0hzW8']Sixty Symbols - Polarisation[/URL] For me this is still arm-waving, but he does say that he could explain it mathematically, if only we could understand him! Even though I can't give a decent account of it, the alignment of molecules or chemical (ie. electrical) bonds seems pretty likely the key. The main materials for polarisers are polymers with oriented molecules, crystals with very ordered electronic lattices, or grids of conductors (as shown in his experiment with microwaves). There is, incidentally, another way (at least) of polarising light. That is to use reflection at the interface of two transparent media. You can take microscope slides and tilt them at the Brewster angle for that glass and pass the beam of light through. There is no absorption, but the transmitted and reflected light has opposite polarisation. Doesn't really help that much, as I can't find a satisfying classical explanation and the quantum one seems just as complex as for filters. I don't know if any of that helps. If I ever locate a decent explanation of how polaristion occurs in any material, I'll post again. Perhaps a Quantum Physicist might attempt an explanation that we could understand - or maybe you'll become one yourself soon! Too late for me: I'm forgetting even that which I used to know (or mistakenly believed I knew, if Unzicker is right!) [/QUOTE]
Insert quotes…
Post reply
Forums
Physics
Classical Physics
Optics
Trying to Understand the Polarization of light
Back
Top