User Name
Password

Go Back   Planetarion Forums > Non Planetarion Discussions > General Discussions

Reply
Thread Tools Display Modes
Unread 23 Aug 2005, 14:05   #1
Radical Edward
Registered User
 
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
Radical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriend
Snell's law and isotropic materials

I have been puzzling over a little problem I have. If a ray of light is travelling from one material (a) to another (b) then given that we know the angle in (a) one calculates the refracted angles using snell's law - easy enough. but for an anisotropic material, the refractive index is a function of angle. now in the case where the ray is travelling from an anisotropic material to isotropic, it is easy to work out the angle in the isotropic (just the old snell's law again) but if a ray is travelling from isotropic to anisotropic, or even anisotropic to anisotropic, then I am at a loss as to how to calculate the angle in material (b)

anyone got any ideas how to do this?
__________________
I think it's time we blow this scene, get everybody and the stuff together..........

ok 3..... 2..... 1.. let's jam

Last edited by Radical Edward; 24 Aug 2005 at 13:42.
Radical Edward is offline   Reply With Quote
Unread 23 Aug 2005, 15:51   #2
Jennifer
Destroyer of Worlds
 
Join Date: Feb 2002
Posts: 552
Jennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet society
Re: Snell's law and isotropic materials

Don't you have all your 'an's in the wrong places?
__________________
“In spite of the roaring of the young lions at the Union, and the screaming of the rabbits in the home of the vivisect, in spite of Keble College, and the tramways, and the sporting prints, Oxford still remains the most beautiful thing in England, and nowhere else are life and art so exquisitely blended, so perfectly made one.”
Jennifer is offline   Reply With Quote
Unread 23 Aug 2005, 15:54   #3
Jennifer
Destroyer of Worlds
 
Join Date: Feb 2002
Posts: 552
Jennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet society
Re: Snell's law and isotropic materials

When you say you 'know the angle' of the ray in material (a), at which point are you measuring the angle? At the point it reaches the boundary?
__________________
“In spite of the roaring of the young lions at the Union, and the screaming of the rabbits in the home of the vivisect, in spite of Keble College, and the tramways, and the sporting prints, Oxford still remains the most beautiful thing in England, and nowhere else are life and art so exquisitely blended, so perfectly made one.”
Jennifer is offline   Reply With Quote
Unread 24 Aug 2005, 13:41   #4
Radical Edward
Registered User
 
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
Radical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriend
Re: Snell's law and isotropic materials

Quote:
Originally Posted by Jennifer
Don't you have all your 'an's in the wrong places?
oops. I'll swap them all round.
__________________
I think it's time we blow this scene, get everybody and the stuff together..........

ok 3..... 2..... 1.. let's jam
Radical Edward is offline   Reply With Quote
Unread 24 Aug 2005, 13:43   #5
Radical Edward
Registered User
 
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
Radical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriend
Re: Snell's law and isotropic materials

Quote:
Originally Posted by Jennifer
When you say you 'know the angle' of the ray in material (a), at which point are you measuring the angle? At the point it reaches the boundary?
yeap.
__________________
I think it's time we blow this scene, get everybody and the stuff together..........

ok 3..... 2..... 1.. let's jam
Radical Edward is offline   Reply With Quote
Unread 24 Aug 2005, 13:44   #6
Radical Edward
Registered User
 
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
Radical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriend
Re: Snell's law and isotropic materials

to all the people who negrepped me, I just thought I would say that I posted this on this forum because I know there are clever people like Jennifer and MrL who might have an idea as to what to do.
__________________
I think it's time we blow this scene, get everybody and the stuff together..........

ok 3..... 2..... 1.. let's jam
Radical Edward is offline   Reply With Quote
Unread 24 Aug 2005, 14:13   #7
NEWSBOT3
NEWSBOT
 
Join Date: Dec 2000
Location: The enby cave!
Posts: 4,872
NEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriendNEWSBOT3 needs a job and a girlfriend
Re: Snell's law and isotropic materials

thats a fair point, but wouldn't you have been better just sending a pm to those two ?
__________________
[20:27:47] <nodrog-aawy> **** i think my housemate just caught me masturbating
[11:25:32] <idimmu> you are a little piggy arent you
[13:17:00] <KaneED> i'm so closet i'm like narnia
__________________
Pretty parks and funky scrap metal things here
NEWSBOT3 is offline   Reply With Quote
Unread 24 Aug 2005, 14:20   #8
Radical Edward
Registered User
 
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
Radical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriendRadical Edward needs a job and a girlfriend
Re: Snell's law and isotropic materials

maybe, but there might be other physicists that I am unaware of, or it might be one of those obscure topics that people spontaneously take an interest in (though I doubt it)
__________________
I think it's time we blow this scene, get everybody and the stuff together..........

ok 3..... 2..... 1.. let's jam
Radical Edward is offline   Reply With Quote
Unread 24 Aug 2005, 22:06   #9
Jennifer
Destroyer of Worlds
 
Join Date: Feb 2002
Posts: 552
Jennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet societyJennifer is a pillar of this Internet society
Re: Snell's law and isotropic materials

Do you have an explicit function for the refractive index? You might find it easier to consider wavefronts rather than rays, then there's a whole subject dedicated to it. I never had a particularly strong grasp of non-linear optics, but if you can be more specific about what it is you're trying to do, I might be able to help.
__________________
“In spite of the roaring of the young lions at the Union, and the screaming of the rabbits in the home of the vivisect, in spite of Keble College, and the tramways, and the sporting prints, Oxford still remains the most beautiful thing in England, and nowhere else are life and art so exquisitely blended, so perfectly made one.”
Jennifer is offline   Reply With Quote
Unread 24 Aug 2005, 22:13   #10
queball
Ball
 
queball's Avatar
 
Join Date: Oct 2001
Posts: 4,410
queball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so littlequeball contributes so much and asks for so little
Re: Snell's law and isotropic materials

Does one have to worry about polarisation or is it just lines and tensors?

If desperate, you could define the full 3D problem using Fermat's principle and solve it numerically. I think a basic 2D problem (where the boundary is aligned with the principal axes of the permittivity tensors) is isomorphic to an isotropic problem by scaling.
__________________
#linux
queball is offline   Reply With Quote
Unread 25 Aug 2005, 01:28   #11
Thermodynamics
Powering your life...
 
Join Date: Dec 2004
Location: Dublin
Posts: 400
Thermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to behold
Re: Snell's law and isotropic materials

Hmmm.... personally I'd need a bit of help from the advanced amterails physics guys to take a solely mathematical approach- but surely an approach more experimental in nature could lead to a better understanding of the situation?

Now, let's *try* the conceptual approach.

An ansiotropic material has 21 elastic constants while an Isotropic only has 2 of these independant variables- Young's modulus E and the Poisson's ratio v.

I won't list the 21 ansitropic ones [not that i can remember...lol]

These 2 heavily ifluence the stiffness and compliance matrices- ensuring the material properties are independent of direction. And isotropic tends to have a constant refractive index- eg. air.

Ansitropic is where it gets tricky alright.

Ansitropic tends to be split up into 2 categories- uniaxial and biaxial:

Uniaxial- tetragonal and hexagonal crystal systems, generally occurs in crystals and fragile, brittle plastics.
Each wave length that passes through is characterised by 2 extreme refractive indices- this is why a crystal will show so many colours, each wavelength travels at a differant speed and hence the ray gets split up.

Biaxial- triclinic, monoclinic, and orthorhombic crystal systems- This one has 3 extreme refractive indexes with the 2nd be the exacy intermediate of the two.

So that was actually all relevant- :-p

What should happen is that each wavelength is dispersed and then undergoes refraction and each ray takes a differant path and needs to be calculated sepreately- which is where the advanced materials physichists come in!

Hope it has been of some help- i'm a bit drunk so didn't exactly offer the clearest of posts to aid you!
__________________
Reality is only a perception.
Thermodynamics is offline   Reply With Quote
Unread 25 Aug 2005, 01:30   #12
Thermodynamics
Powering your life...
 
Join Date: Dec 2004
Location: Dublin
Posts: 400
Thermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to beholdThermodynamics is a splendid one to behold
Re: Snell's law and isotropic materials

PLease forgive grammar+speeling, again I'm a little drunk, apologies.
__________________
Reality is only a perception.
Thermodynamics is offline   Reply With Quote
Unread 25 Aug 2005, 02:00   #13
Boogster
I dunno...
 
Boogster's Avatar
 
Join Date: Jun 2003
Location: manchester
Posts: 1,502
Boogster has much to be proud ofBoogster has much to be proud ofBoogster has much to be proud ofBoogster has much to be proud ofBoogster has much to be proud ofBoogster has much to be proud ofBoogster has much to be proud ofBoogster has much to be proud of
Re: Snell's law and isotropic materials

Goodness, this is all a tad confusing.
__________________
He shall drink naught but brine, for I'll not show him / Where the quick freshes are.
Boogster is offline   Reply With Quote
Unread 27 Aug 2005, 03:00   #14
JetLinus
Friendly geek of GD :-/
 
JetLinus's Avatar
 
Join Date: Nov 2000
Location: On my metal roid
Posts: 923
JetLinus has much to be proud ofJetLinus has much to be proud ofJetLinus has much to be proud ofJetLinus has much to be proud ofJetLinus has much to be proud ofJetLinus has much to be proud ofJetLinus has much to be proud ofJetLinus has much to be proud ofJetLinus has much to be proud ofJetLinus has much to be proud of
Arrow Re: Snell's law and isotropic materials

Quote:
Originally Posted by Radical Edward
maybe, but there might be other physicists that I am unaware of, or it might be one of those obscure topics that people spontaneously take an interest in (though I doubt it)
I'm a physics-wannabe failing maths right now, but doing ok in physics because of a "solid feeling" ;-)
1st year at uni is almost over now.

Reading this thread could've made me more clever!
__________________
[»] Entropy increases! :-/
JetLinus is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Forum Jump


All times are GMT +1. The time now is 22:56.


Powered by vBulletin® Version 3.8.1
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2002 - 2018