Joel Franklin, Computational Methods for Physics, Cambridge University Press, 2016.Į. DeVries, A First Course in Computational Physics, Jones Bartlett Learning, 2011. Tao Pang, An Introduction to Computational Physics, Cambridge University Press, 2006. Sharma, Optics Principles and Applications, Academic Press Elsevier, 2006. Goodman, Introduction to Fourier Optics, McGraw-Hill, 1996. Pragati Ashdhir, Jyoti Arya, Chaudhary Eksha Rani, and Anshika, Exploring the fundamentals of fast Fourier transform technique and its elementary applications in physics, European Journal of Physics, Vol.42, No.6, p.065805, Sep 2021. Scilab Enterprises et al., Scilab: Free and Open Source Software for Numerical Computation, Scilab Enterprises, Orsay, France, 3, 2012. Marsh, Diffraction patterns of simple apertures, Journal of the Optical Society of America, Vol.64, No.6, 798, June 1974. II, Optica Acta: International Journal of Optics, Vol.20, No.7, pp.549–563, July 1973. Komrska, Fraunhofer diffraction at apertures in the form of regular polygons. P B Sunil Kumar and G S Ranganath, Geometrical theory of diffraction, Pramana, Vol.37, No.6, pp.457–488, December 1991. The target group are undergraduate students of physics and engineering sciences. A computational approach has far greater flexibility and scope in exploring different aspects of a given problem compared to a corresponding analytical treatment of the same. The article aims to highlight the importance and ease of using computational methods in problem-solving. The results presented in this article 1 agree fairly well with theoretical predictions and with those reported in the literature. Some apertures with geometrical shapes, such as triangles, trapeziums, hexagons and pentagons, have been analysed in the past. The basic apertures like single slits, double slits, multiple slits, rectangular and circular are generally treated in theory as a part of any wave optics undergraduate course. Subsequently, the discrete Fourier transform technique is used to generate Fraunhofer diffraction patterns due to the simulated planar apertures. The computational technique of discrete convolution is used to simulate planar diffracting apertures of varied geometry. The results obtained indicate that this technique should prove quite useful in the measurement of small particles, aerosols, fog droplets, etc.It is one of the basic principles of Fourier Optics that the field distribution in far-field or Fraunhofer diffraction pattern due to a planar diffracting aperture is proportional to the Fourier transform (FT) of field distribution in the aperture plane. Using a pulsed ruby laser as a source, diffraction patterns of moving particles have been photographed. The film planes are set at known distances from the image plane so that Fraunhofer diffraction patterns of the individual particles are recorded. A second lens re-transforms the remaining pattern to produce an image of the original particles. This term, which represents the interference between the light diffracted by the particle and the coherent background, may be removed by spatially filtering the diffraction pattern formed in the focal plane of a lens. The intensity distribution in the Fraunhofer pattern consists of several terms but the dominating one involves the Airy pattern of a circular aperture multiplied by a sine function, which is independent of the size of the particles. The plane in which the diffraction is recorded is at a sufficient distance from the plane containing the particles for the ap-proximation of Fraunhofer diffraction to be made-but not in the focal plane of a lens. Diffraction by opaque and transparent particles which present a circular cross-section to a collimated quasi-monochromatic beam of light is discussed theoretically and experimentally.
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