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# Polarisation watch

1. Could anyone explain polarisation to me? The book uses the analogy of tying a rope to a post and shaking it...which seems to make things even less clear for me. (AS - OCR A)

I also need to know how it relates to its uses: sunglasses/stresses in materials/ LCDs
2. As I understand it, polarisation is caused by the atoms having different electronegativities, i.e. the electrons of one atom are held more strongly by the nucleus than those of the other atom. This makes the atom with the higher electronegativity have a slightly negative charge and the other one a slightly positive charge.
Sorry, I don't know how it relates to those other things.
3. I think LS meant polarisation of waves (specifically visible light), not polarisation of chemical bonds.
4. (Original post by rts)
I think LS meant polarisation of waves (specifically visible light), not polarisation of chemical bonds.
Yeah, this is for physics and is the chapter for 'superposition of waves' (well, I think it's that chapter).
5. polarisation - confinement of a wave into a single wavelenght
example,use two polaroids,put two of them and rotate it at 90 degrees,the lights cancels out and it gives darkness..

polarisation in sunglasses is basically the cancellation of harmful wavelenghts such as the UV light from the sun so that it doesnt reach the eyes.
6. (Original post by MalaysianDude)
polarisation - confinement of a wave into a single wavelenght
example,use two polaroids,put two of them and rotate it at 90 degrees,the lights cancels out and it gives darkness..

polarisation in sunglasses is basically the cancellation of harmful wavelenghts such as the UV light from the sun so that it doesnt reach the eyes.
and in sunglasses you'd have just one plane, otherwise you'd see nothing!
7. (Original post by hihihihi)
and in sunglasses you'd have just one plane, otherwise you'd see nothing!
oh man...you can have two planes...as long as both of them is not rotated at 90 degrees,or you`ll see nothing
8. (Original post by MalaysianDude)
oh man...you can have two planes...as long as both of them is not rotated at 90 degrees,or you`ll see nothing
ah yes. so how many planes would they normally have?
9. I'm still not getting this...oh well, probably due to over-revising (this chapter ahsn't been taught, I'm doing my best to go through it).

But thanks everyone for trying
10. Only transverse waves can be polarised becuase there are two planes of vibration at right angles to the direction that the wave is travelling in - electromagnetic and magnetic.

When a wave is polarised the vibrations are restricted to only one plane of vibration. If there are crossed polaroids, i.e. one polaroid at 90 degrees and the next at 180 degrees then the wave exiting the second polaroid will have zero amplitude as no vibrations will occur.

Hope this has helped a little
11. Thanks Erased Citizen - it helped a little - I think it'll just be one of those things where I just 'learn' it without much understanding. But your summary is far clearer than that of the text book

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