So light can be polarised, huh... This means that the light only travels in one plane. So there's a slit (what material?) that polarises light as it passes through...? "The transverse vibrations of a light wave are a varying electric field (E) and a varying magnetic field (B) which are perpendicular to each other..." What on earth does this mean? I thought polarised had something to do with magnets, I am so confused. "Polaroids contain special crystals... Other vibrations are absorbed" Right, so light not in the plane (the plane that somehow corresponds to the slit in some unknown way) is absorbed by the polariod material (slit) so... well, how... I mean, this slit would have energy building up in it... would it become warmer??? How does it lose the energy that it's crystals absorbed. Yeah i hope you guys can help this confused kid out, my A level Physics teach ain't the best at explaining things...
There are certain materials (natural and manmade) that DO polarize light. These materials preferentially allow light to travel in select directions. One natural example is the mineral calcite (there are others too) that exhibits such phenomenon. Impinging light packets, vibrating in multiple, random directions is constrained to 'follow' the crystal structure. Calcite separates the impinging, multi-directional vibration light into what are called 'e' rays and 'o' rays due to the anisotropic structure of calcite - anisotropy? . . . that is, the material has more than one refractive index (2 in calcite) as an inherent characteristic the crystal structure, due to molecular arrangements. This is why calcite, by 'splitting' the impinging light into two 'rays' (one slower, and one faster) forms a 'double image' when objects are viewed through a clear crystal. Isotropic materials, by definition, have only one refractive index that depends primarily upon composition of the material (e.g., a glass lens is isotropic; some minerals are also isotropic). BTW: For a single light 'ray' the B (magnetic) and E (electric) fields DO vibrate perpendicular to each other. Extra points for this one: Since all light propogates at c in a vacuum (or at velocity 'v' in a material, where v depends on refractive index), how fast (v') are the B and E field vibrations that are moving at right angles to each other and relative to the propogation of the ray? And yes, the comparison to slit geometry is apropos . . . but that's another discussion . . . .
Yes for each ray There are lots of different materials that are used in glass silver is used. View attachment 5819 Sure but not that you would notice. Another thing to keep in mind is that the light wave is polarized through the electric field and not the magnetic field. In other words the light waves electric field is what is attenuated by the material of the polarizer.
well now i have a new idea of light: it's actually two waves! Ok, these waves vibrate at the same frequency as each other because they are one wave... but then does polarisation only allow one of them, the electric field through? or is the magnetic field completely unaffected? If light cannot pass through the polarised material because I had two such slits, one of them was rotated 90 degrees from the other, pressed against each other... this let's no visible light through, that would be my observation. But... does this mean the electric waves are stopped (absorbed) , but the magentic waves, which we can't see, pass through??? and as for that question, what speed they vibrate at? well v = f (lamda) so the speed of light divided by the wavelength of light, which i don't really know, i think it's around 400-650 nanometers or something? (still confused)
A light wave has a varing electric field component and a varing magnetic field component. It is one wave. They cannot be separated into a magnetic and electric component that being said the answer is the latter above - the magnetic field is not affected by the polarizer and the light wave that passes through the polarizer is just as it was before the polarizer. Polarizers are made of a grid. If you look through 2 polarizers that have the grides 90 degrees out of phase then you will not see any light through them. Don't think of photons or light waves as having 2 separate fields or you will confuse yourself into thinking 1/2 of a light wave is possible - it ain't. When the electric field interacts (is attenuated) by the polarizer the light wave is absorbed by an electron there is no residual magnetic field or anything else left ouve. The speed of light is constant so the wavelength and the frequency vary by the following relationship. \(f = \frac{c}{\lambda} \)
i'm starting to get a feel for this, thanks for your help so far guys Please Register or Log in to view the hidden image! so... the apropos slits only allow light to travel through in one plane, the light is said to be polarised, all other light is 'absorbed' by electrons, the electic waves and the magnetic waves, which make up a whole light wave. but how exactly is light polarised by this material? is it made up in such a way that the particles/molecules 'guide' the light through, and all other light is absorbed? so i think then that the intensity of polarised light would be about... half that of un-polarised?
There is a wealth of information on the net about polarization of light. Here is a simple discussion.
thanks for all your help guys i think i get it now Please Register or Log in to view the hidden image!
