Understanding Brewster Angle & Polarised Beams

[kame]

Hi! I didn't understand how the brewster angle works. Why do I have a polarised beam? Do I need electromagnetism to understand this?

 

[dacruick]

To understand why this happens you need electromagnetic theory. But to apply the concept you don't. What exactly are you looking for in an answer here?

 

[kame]

I need the electromagnetic explanation :)

Thanks in advance

 

[dacruick]

I can't answer that for you, I don't know it. You'd do best to look at wikipedia at this point. I also don't think that this is going to be cut and dry.

 

[kame]

Wikipedia? I didn't find it. :(

 

[Nabeshin]

I'm assuming you have some knowledge of the fresnel equations, which deal with how an electromagnetic wave interacts with the interface between two media. If you don't know this, then it is much more difficult to accurately describe the Brewster angle!

Any ways, from the fresnel equations it is easy to see when the reflected portion of the electric field is zero. Trivially, there is the case where n1=n2, that is, the two media are optically identical and of course there is no reflection. The second case is the brewster angle, for which $$n_2 / n_1 = tan \theta_B$$. Another way of thinking about this is that if you have a beam which is a mixture of polarizations parallel to and perpendicular to the interface, the reflected portion of the beam parallel is completely zero, i.e. the reflection is polarized perpendicular to the interface. Equivalently, if you shine a beam which is parallel polarized on the interface, there will be no reflected beam at all!

Does that help at all? If what I've said doesn't make sense I suggest you look back at the Fresnel equations and perhaps read the wiki article and see if you still have any questions =)

 

[kame]

I have to read about the fresnel formula. Thanks!

 

[dacruick]

If you run python I have a little program that will take 2 refractive indices and spit out the reflection coefficients for each angle of incidence from 0-90. Let me know if you want it.

 

[Vanadium 50]

Wikipedia? I didn't find it. :(

That's surprising, since they have an entry on it.

 

[kame]

@dacruick I love Python! Please send me the file.
This is my Python-Blog :) kkaammee.blogspot.com/

 

[kame]

@Vanadium50
Can you show me where they write why the reflected beam is polarised?

 

[Vanadium 50]

That would be the first paragraph. And the second, third, fouth, fifth, sixth seventh and last. And the first and last figure.

The advice to look at the Wikipedia article was a good one. Really.