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The Classical Double Slit Interference Experiment: A New Geometrical Approach
Issue:
Volume 7, Issue 1, March 2019
Pages:
1-9
Received:
2 March 2019
Accepted:
9 April 2019
Published:
7 May 2019
Abstract: The double slit experiment was first conceived of by the English physician-physicist Thomas Young in 1801. It was the first demonstrative proof that light possesses a wave nature. In this experiment, light is made to pass through two very narrow slits that are spaced closely apart and a screen placed on the other side captures a pattern of alternating bright and dark stripes called fringes, formed as a result of the interference of ripples of light emanating from either slit. The relative positions and intensities of the fringes on the screen can be calculated by employing two assumptions that help simplify the geometry of the slit-screen arrangement. Firstly, the screen to slit distance is taken to be larger than the inter-slit distance (far field limit) and secondly, the inter-slit distance is taken to be larger than the wavelength of light. This conventional approach can account for the positions and intensities of the fringes located in the central portion of the screen with a fair degree of precision. It however, fails to account for those fringes located in the peripheral portions of the screen and also, is not applicable to the case wherein the screen to slit distance is made comparable to the inter-slit distance (near field limit). In this paper, the original analysis of Young’s Experiment is reformulated using an analytically derived hyperbola equation, which is formed from the locus of the points of intersections of two uniformly expanding circular wavefronts of light that emanate from either slit source. Additionally, the shape of the screen used to capture the interference pattern is varied (linear, semicircular, semielliptical) and the relative positions of the fringes is calculated for each case. This new approach bears the distinctive advantage that it is applicable in both the far field and the near field scenarios, and since no assumptions are made beyond the Huygens-Fresnel principle, it is therefore, a much more generalized approach. For these reasons, the author suggests that the new analysis ought to be introduced into the Wave Optics chapter of the undergraduate Physics curriculum.
Abstract: The double slit experiment was first conceived of by the English physician-physicist Thomas Young in 1801. It was the first demonstrative proof that light possesses a wave nature. In this experiment, light is made to pass through two very narrow slits that are spaced closely apart and a screen placed on the other side captures a pattern of alternat...
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Germanium Based Two-Dimensional Photonic Crystals with Square Lattice
Fairuz Aniqa Salwa,
Muhammad Mominur Rahman,
Muhammad Obaidur Rahman,
Muhammad Abdul Mannan Chowdhury
Issue:
Volume 7, Issue 1, March 2019
Pages:
10-17
Received:
11 March 2019
Accepted:
26 April 2019
Published:
15 May 2019
Abstract: Using the plane-wave expansion method, we study the polarization-dependent photonic band diagrams (transverse electric and transverse magnetic polarizations), surface plots, gap maps etc. of the two-dimensional photonic crystals with square lattice of germanium rods in air and vice versa. The obtained graphs for the two possible combinations are presented in this paper. All the results depict clear photonic band gaps. We describe the conditions for the largest TE and TM band gaps too. The square lattice of Ge rods in air offers a large TE photonic band gap of 48.02% (for rod radius of r = 0.2μm). Then we localize the TE mode by introducing a point defect and a line defect in the crystal. The point defect act as a resonator and the line defect act as a waveguide. The finite-difference time-domain analysis of the localized defect modes is presented also.
Abstract: Using the plane-wave expansion method, we study the polarization-dependent photonic band diagrams (transverse electric and transverse magnetic polarizations), surface plots, gap maps etc. of the two-dimensional photonic crystals with square lattice of germanium rods in air and vice versa. The obtained graphs for the two possible combinations are pr...
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Antillatoxin (ATX) Time–Resolved Absorption and Resonance FT–IR and Raman Biospectroscopy and Density Functional Theory (DFT) Investigation of Vibronic–Mode Coupling Structure
Alireza Heidari,
Jennifer Esposito,
Angela Caissutti
Issue:
Volume 7, Issue 1, March 2019
Pages:
18-27
Received:
8 April 2019
Accepted:
3 June 2019
Published:
13 July 2019
Abstract: Antillatoxin (ATX) is a potent lipopeptide neurotoxin produced by the marine cyanobacterium Lyngbya majuscula. ATX activates voltage–gated sodium channels, which can cause cell depolarisation, NMDA–receptor over activity, excess calcium influx and neuronal necrosis. Parameters such as FT–IR and Raman vibrational wavelengths and intensities for single crystal Antillatoxin are calculated using density functional theory and were compared with empirical results. The investigation about vibrational spectrum of cycle dimers in crystal with carboxyl groups from each molecule of acid was shown that it leads to create Hydrogen bonds for adjacent molecules. The current study aimed to investigate the possibility of simulating the empirical values. Analysis of vibrational spectrum of Antillatoxin is performed based on theoretical simulation and FT–IR empirical spectrum and Raman empirical spectrum using density functional theory in levels of HF/6–31G*, HF/6–31++G**, MP2/6–31G, MP2/6–31++G**, BLYP/6–31G, BLYP/6–31++G**, B3LYP/6–31G and B3LYP6–31–HEG**. Vibration modes of methylene, carboxyl acid and phenyl cycle are separately investigated. The obtained values confirm high accuracy and validity of results obtained from calculations.
Abstract: Antillatoxin (ATX) is a potent lipopeptide neurotoxin produced by the marine cyanobacterium Lyngbya majuscula. ATX activates voltage–gated sodium channels, which can cause cell depolarisation, NMDA–receptor over activity, excess calcium influx and neuronal necrosis. Parameters such as FT–IR and Raman vibrational wavelengths and intensities for sing...
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