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Fiber structure helps to acquire knowledge about fiber an its composition for improving use of fiber in textile.

Measuring of fiber structure manly introduce the fiber composition, length, weight, thickness, fineness, flexibility, stability etc.

Methods for measuring of fiber structure: Optical and X-ray diffraction Optical microscopy Electron microscopy and electron diffraction Optical properties Thermal analysis Density

When a beam of light is passed through a photographic slide, the light is scattered in many directions.

By using a lens in the right place, we can recombine this scattered information about the picture into an image on a screen.

Example: There is a characteristic diffraction pattern from a single slit. The difference between the image that must be focused at a particular place and the angular diffraction pattern that can be intercepted anywhere is shown in Fig.

The use of polarized light in either of the above two techniques changes the pattern and thus, in principle, increases the available information about structure if it can be interpreted.

A diffraction grating of regularly spaced lines, illuminated normally by parallel light, will give a set of fringes, with the maxima of the bright bands at angles φ defined by the relation: nλ = a sinφ Where n is an integer, λ the

wavelength of light and a the spacing of the lines in the grating.

X-radiation (composed of X-rays) is a form of electromagnetic radiation.

X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz(3×1016 Hz to 3×1019 Hz) and energies in the range 100 eVto 100 keV.

The wavelengths are shorter than those of UV rays and longer than those of gamma rays.

In Bragg’s law, when x-rays are scattered from a crystal lattice, peaks of scattered intensity are observed which correspond to the following conditions: The angle of incidence = angle of

scattering. The path length difference is equal to

an integer number of wavelengths.

The condition for maximum intensity contained in Bragg's law above allow us to calculate details about the crystal structure, or if the crystal structure is known, to determine the wavelength of the x-rays incident upon the crystal. n λ = 2d sin θ

The condition that a particular reflection should occur is that the layer of atoms should make the required angle with the X-ray beam. This will happen for a series of orientations of the crystals distributed around a cone. The X-rays will be reflected around a cone of twice this angle, as shown in Fig.

Electron diffraction refers to the wave nature of electrons. However, from a technical or practical point of view, it may be regarded as a technique used to study matter by firing electrons at a sample and observing the resulting interference pattern. This phenomenon is commonly known as the wave-particle duality, which states that the behavior of a particle of matter can be described by a wave.

Normal optical microscope we can find out up to 0.5 Å only. By using of electron microscope we can able to find out up to 5 Å. The rays from electron source are condensed on the specimen. Here only dry sample can be examined. Contrast in the image depends on the variation in scattering of the

electrons by parts of the specimen of differing density.

Electron microscope method is better to examining the surface of the fiber

The main use of EM in fiber science has been in the range of medium to high magnification, which is near or beyond the limit of the microscope .