Determination of the refractive index of fibres using the modified area method: I. Homogeneous fibres |
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Authors: | T Z N Sokkar M A El-Bakary |
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Institution: | Physics Department, Faculty of Science, Mansoura University, Mansoura 35516, Egypt |
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Abstract: | The mathematical formulae for determining the mean refractive indices and birefringence of homogeneous fibres are modified. This modification depends on calculating the area under the fringe shift and cross-sectional area of homogeneous fibres having nearly circular cross-sectional area taking the refraction of the incident light beam by the fibre into consideration. The mathematical analysis for two-beam and multiple-beam interferometric techniques is dealt with. These formulae are applied to polypropylene fibres with draw ratios of 3.5 and 4 using the two techniques. A comparison between the results when using the new formulae and when neglecting the refraction has been studied. The diffraction of a He–Ne laser beam is used for determining the shape of the cross-sectional area of these fibres. Microinterferograms are given for illustration. |
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Keywords: | Two-beam interference Multiple-beam Fizeazu fringes Refractive indices Refraction Area method Polypropylene fibres |
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