Re: polarizing microscope for the refractive index calculation

On 2 Dec 2003 23:34:37 -0800, [EMAIL PROTECTED] (tzavalas) wrote:


>I just want to know how these bizzare colored images coming out of a
>polarized microscope can be translated to n???


Plain and simple, the answer to your question, as far as I know,  is
that you cannot obtain the refractive index of your polymer by direct
observation of the colors viewed with a polarized light microscope.
You can determin that there is birefingence and you can measure
retardation of the extra ordinary light ray.  

Crystalographers have a method of measuring the retardation of a
birefingent this section of rock crystal using clibrateed rotating
stages, poliarzation filters and various compensators with known
retardation values.  The retardation is a consequence of the
difference in refractive index which splits one incident light ray
into the ordinary and exraordinary rays..This method can be applied to
measuring the retardation of the polymer film 

Crystalographers then refer to the Michael-Levy chart, which
summarizes known data concerning  the thickness of the sample with the
colors observed and the retardation.  From these physical properties
they can charaxcterize or identify the mineral.  They do not measure
refractive indx.

The physical and chemical differences between the minerals for which
this method was deveolped and your polymers precludes application of
this exact method.  I don't thind there is an equivalent to a
Michael-Levy chart for polymers.    

The measurements that you desire are made with other instruments that
simultaneously measure Brewster's angle and/orr other
spectophotometric properties. These measurments are then processed by
computer to give the refractive index..   If the measurments could be
made simply  with polarized light microscopes there would not be a
need for other expensive equipment.    

See 

http://www.osa.org/meetings/archives/2001/oic/techpro/postshow/giant.pdf

for additional discussion and references..
 .