Swapan K Saha – författare

Waves and oscillations are found in large scales (galactic) and microscopic scales (neutrino) in nature. Their dynamics and behavior heavily depend on the type of medium through which they propagate.Waves and Oscillations in Nature: An Introduction clearly elucidates the dynamics and behavior of waves and oscillations in various mediums. It presents different types of waves and oscillations that can be observed and studied from macroscopic to microscopic scales. The book provides a thorough introduction for researchers and graduate students in assorted areas of physics, such as fluid dynamics, plasma physics, optics, and astrophysics. The authors first explain introductory aspects of waves and electromagnetism, including characteristics of waves, the basics of electrostatics and magnetostatics, and Maxwell’s equations. They then explore waves in a uniform media, waves and oscillations in hydrodynamics, and waves in a magnetized medium for homogeneous and nonhomogeneous media. The book also describes types of shock waves, such as normal and oblique shocks, and discusses important details pertaining to waves in optics, including polarization from experimental and observational points of view. The book concludes with a focus on plasmas, covering different plasma parameters, quasilinear and nonlinear aspects of plasma waves, and various instabilities in hydrodynamics and plasmas.

This book deals with the fundamentals of wave optics, polarization, interference, diffraction, imaging, and the origin, properties, and optical effects of turbulence in the Earth's atmosphere. Techniques developed during the last few decades to overcome atmospheric image degradation (including passive methods, speckle interferometry in particular, and active methods such as adaptive optics), are highlighted. Also discussed are high resolution sensors, image processing, and the astronomical results obtained with these techniques.

Interferometric observations need snapshots of very high time resolution of the order of (i) frame integration of about 100 Hz or (ii) photon-recording rates of several megahertz (MHz). Detectors play a key role in astronomical observations, and since the explanation of the photoelectric effect by Albert Einstein, the technology has evolved rather fast. The present-day technology has made it possible to develop large-format complementary metal oxide–semiconductor (CMOS) and charge-coupled device (CCD) array mosaics, orthogonal transfer CCDs, electron-multiplication CCDs, electron-avalanche photodiode arrays, and quantum-well infrared (IR) photon detectors. The requirements to develop artifact-free photon shot noise-limited images are higher sensitivity and quantum efficiency, reduced noise that includes dark current, read-out and amplifier noise, smaller point-spread functions, and higher spectral bandwidth. This book aims to address such systems, technologies and design, evaluation and calibration, control electronics, scientific applications, and results.One of the fastest growing applications is signal sensing, especially wavefront sensing for adaptive optics and fringe tracking for interferometry, which is important for long-baseline optical interferometry. The coherence time of the atmosphere is a highly variable parameter. Depending upon the high velocity wind, it varies from <1 ms to 0.1 s. The exposure times are to be selected accordingly, to maximize the signal-to-noise ratio, as well as to freeze the fringe pattern. A large-format photon-counting system, which is an essential tool in the application of optical interferometric imaging, allows accurate photon centroiding and provides the dynamic range needed for measurements of source characteristics. The advent of high-quantum efficiency photon-counting systems vastly increases the sensitivity of high-resolution imaging techniques. Such systems raise the hope of making diffraction-limited images of objects as faint as ~15–16 m_v (visual magnitude).This book deals with the fundamentals of the important aspects of high-resolution imaging, such as electromagnetic radiations, particularly, optical wavelengths and their distortions due to optical elements and Earth’s atmosphere while passing through a detector; semiconductor physics; lasers; fiber optics; photon-detection process; photodetectors; charge-transfer devices; photon-counting devices in visible wavelength; radiation detectors in infrared wavelengths; and detecting systems for high energies.