الفهرس 
Introduction
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Abstract
Optical properties of fibres, like refractive index and birefringence, are important in testing, identifying, and grading of fibres, beside helping to elucidate their structure. In the present work two methods were used for the determination of refractive indices and birefringence for different layers of polypropylene and polyethylene fibres. First the Beckeline method was used for the measurement of the refractive indices of the outer layer (skin) of the fibre.