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Characterization Techniques for Nanomaterials: Research and Opportunities for Potential Biomedical Applications
Published in Deepak Kumar Verma, Megh R. Goyal, Hafiz Ansar Rasul Suleria, Nanotechnology and Nanomaterial Applications in Food, Health, and Biomedical Sciences, 2019
S. P. Suriyaraj, Deepak Kumar Verma, H. Bava Bakrudeen, Y. Antony Prabhu, S. Vaidevi, B. Ramiya, V. Monika, J. Prasana Manikanda Kartik, K. Chandraraj
X-ray is a form of electromagnetic radiation having wavelength range from 0.01 to 10 nm. It was first discovered by German physicist Wilhelm Conrad Rontgen in 1895. They have wavelengths shorter than ultra-violet radiation but longer than gamma rays. Diffraction is a phenomenon where a wave meets an obstacle or a slit and bends around the corner of an interference or aperture.61 Huygens-Fresnel principle states that diffraction describes the interference of waves like light waves, sound waves, electromagnetic waves, X-rays, radio waves and water waves. The 90% of solids available on earth are crystalline in nature and their structure can be interpreted by observing diffraction pattern when X-rays are made incident on them. The electromagnetic spectrum of different scattered wavelength of lights is shown in Figure 5.9.
Waves in Periodic Structures
Published in Vladimir V. Mitin, Dmitry I. Sementsov, An Introduction to Applied Electromagnetics and Optics, 2016
Vladimir V. Mitin, Dmitry I. Sementsov
For a qualitative description of the diffraction phenomena, the method of Fresnel zones is often used. To understand it, let us consider the following example. Let the light wave from a distant source be incident normally on an opaque screen, which has a small circular hole of radius R. Let the observation point P be located on the axis of symmetry and at a distance L from the screen. The wave surfaces of the incident light are parallel to the screen plane and one of them coincides with the screen. In accordance with the Huygens–Fresnel principle, each point of the wave surface becomes a source of secondary spherical waves. All secondary waves interfere at the observation point P, and the result of their interference determines the intensity of the resultant diffracted wave. In order to determine the diffracted wave, it is necessary to split the wave surface within the aperture into rings known as Fresnel zones. The partition is carried out as follows: the distance from the central point O to the observation point P is equal to L. The distance from the boundary of the first zone to the observation point P is chosen to be equal to L+ λ/2. The distance from the boundary between the first zone and the second zone to the observation point P is chosen to be equal to L+ 2(λ/2) and so on (Figure 8.3). Thus, the difference in distance from adjacent Fresnel zone boundaries to the observation point P differs by λ/2, and thus, the vibrations from adjacent zones come to point P with opposite phases.
Basics of Light Propagation
Published in Christoph Gerhard, Optics Manufacturing, 2018
Even though light propagates as a transversal wave, its propagation is usually described and characterized in the form of light rays. Such light rays are given by the perpendicular on the wave front and are the basis of geometrical optics. However, any change in the propagation direction of a light ray, due to refraction or reflection, can be attributed to the Huygens-Fresnel principle, named after the Dutch physicist Christiaan Huygens (1629–1695) and the French physicist Augustin-Jean Fresnel (1788–1827). Geometrical optics thus indirectly takes the wave properties or rather the shape of the wave front of light into account.
Model to describe light scattering by polymer film containing droplets with inhomogeneous anchoring of liquid crystal molecules at the polymer–droplet interface: asymmetry effect in the angular distribution of light
Published in Liquid Crystals, 2019
A. V. Konkolovich, A. A. Miskevich, M. N. Krakhalev, O. O. Prishchepa, A. V. Shabanov, V. Ya. Zyryanov, V. A. Loiko
The asymmetry effect arises owing to inhomogeneity in the anchoring of LC molecules at the droplet surface. The effect has an interference nature and can be explained on the basis of the Huygens–Fresnel principle. In a droplet with inhomogeneous surface anchoring, the distributions of the local refractive indices in regions corresponding to tangential and normal anchoring are different. As a consequence, the phase differences for the secondary waves propagating from these regions in the +θs and −θs directions are different. Interference of these waves at angles +θs and −θs results in different values of the scattered light intensities. The asymmetry effect depends on concentration, size, shape of droplets, refractive indices of LC and polymer matrix, director configuration of LC and illumination conditions.