Stress-induced birefringence parameter

The relationship between the measured relative retardation (R) and the stress-induced birefringence (An) is given by R = fAn (2), in which t is the sample thickness. The stress optical coefficient C is defined by An = Ct (2), in which t is the true stress (t = f/A f is the force in newtons per square millimeter, and A is the cross-sectional area of the network sample). This coefficient is thus simply the slope of the line in a plot of An versus t. Finally, the optical configuration parameter An is defined by... 

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