Re: polarizing microscope for the refractive index calculation

Repeating Decimal <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> in article [EMAIL PROTECTED], George at
> [EMAIL PROTECTED] wrote on 12/1/03 11:52 AM:
> 
> > 
> > "tzavalas" <[EMAIL PROTECTED]> wrote in message
> > news:[EMAIL PROTECTED]
> >> Hello everybody, i´m spiros from greece.
> >> 
> >> I´m taking a course on polymer science and recently I heard that the
> >> non-isotropic substances are not bound to have the same rerfactive
> >> index on all directions. So in the most general case every a sample
> >> bears 2 vertical and one parallel reflactive index. The parallel or
> >> vertical dirctions are regarded in relation to an axis of orientation
> >> of specific groups, like liquid crystals, polymer chains, fibres or
> >> even bonds between atoms etc(which are in the sample and whose
> >> "preference" for a direction is what causes the sample to be
> >> "non-isotropic.")
> >> 
> >> So  in my case, where I have a stretched polymer film, I guess the
> >> same thing is taking place. I know that I can use a polarizing
> >> microscope to calculate the values of the refractive index as the
> >> incident (planar-polarized) on the sample light rotates.
> >> 
> >> BUT I DONT KNOW HOW?????????????
> >> 
> >> thanks in advance, spiros tzavalas.
> > 
> > 
> > It is not an easy subject to learn.  It is even more difficult to teach.
> > There are several good books on the market on optical mineralogy.  I would
> > suggest the following:
> > 
> > Optical Mineralogy: Principles and Practice. Gribble, F., & Hall, A., 1992.
> > UCL Press, 302pp.
> > Major References: 1- Optical Mineralogy, Kerr, P., 1977. McGraw Hill, 442
> > pp. 2- Mineral Optics: Principles and Techniques. Phillips, W.R., 1971. W.H.
> > Freeman & Comp.
> > 3- Student Guidebook for the minerals under the Microscope. Nasir, S., 1997.
> > Colored Manual of Minerals under the Microscope.
> > 
> > Good luck.
> > 
> > 
> Let me add a bit.
> 
> Expression such as "2 vertical and one parallel reflactive index" are almost
> meaningless. There will be ordinary and extraordinary indexes. The meanings
> of these are developed in Born and Wolf, for example.
> 
> While the concepts are clear for crystals (pure minerals), they will
> probably fail for polymers. Polarizations effects in them are more likely to
> depend on induced birefringence from stress and strain.

A more correct way to state this is that polymers have both an
amorphous and a crystalline contribution to any birefringence that is
observed. These portions are more commonly determined using x-ray
techniques rather than microscopy.

What you are looking for are any of the various compensation
techniques such as Babinet, Senarmont, etc. As one poster already
stated, you will be best off working with a good text rather than
trying to learn the techniques from this forum.

John