الفهرس 
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Abstract
1- In this work a simple and accurate interferometric method for measuring
the natural birefringence and its dispersion across the visible region of
spectrum is presented.
2- Although the theoretical and experimental background of the method is
nearly known, the fields of application and data processing approach are
firstly presented. The method is applicable for liquid and solid samples
of fixed thickness all over the slit ofthe spectrograph.
3- A two- term Cauchy dispersion function is most suitable to give
accurate values of the birefringence dispersion, because it is simple and
time saving.
4- The measured birefringence for both a transparent photographic film
and mica sheet decreases with increasing wavelength.
S- The natural birefringence L’in for an anisotropic material is also
evaluated for cellophane sheet by changing its thickness, which is
another simple method for obtaining birefringence for anisorropic
materials.
6- The distribution of the fringes makes it possible to assess the
distribution of the stresses inside the plate. This underlies the optical
method of studying stresses (photoelastic stress analysis). A model
made from a transparent isotropic material is placed between crossed
polarizers. The model is subjected to the action of loads similar to
those, which the article itself wil1 experience. The pattern observed in
transmitted white light makes it possible to determine the distribution
of the strain and also to estimate its magnitude.
7- The induced birefringence produced by a certain stress on an isotropic
material decreases by increasing wavelength and Cauchy’s dispersion
function is achieved. The dispersion increases by increasing applied
stress upon the sample.
8- from the relation between the applied stress and the resulting strain,
which is built upon the displacement in the fringe, Young’s modulus
is evaluated by a simple and accurate method.
9- The stress optical coefficient is obtained, with different wavelengths,
from the relation between the induced birefringence and the applied
stress. The stress optical coefficient depends on the wavelength of the
light and the material used.
10- The bending ofa birefringent plate (Fortepan photographic plate is
used in our experiment) introduces additional birefringence. The
induced birefringence bon increases by decreasing radius of curvature
(i.e., by increasing the applied stress causing curvature.) and the
number of fringes increases and crowds around the center. The natural
birefringence for a Fortepan photographic plate is obtained at infinity
value for the radius of curvature.