28-08-2017, 04:45 PM
Diffraction refers to several phenomena that occur when a wave encounters an obstacle or a cleft. It is defined as the bending of light around the corners of an obstacle or aperture in the region of the geometric shadow of the obstacle. In classical physics, the diffraction phenomenon is described as the interference of the waves according to the Huygens-Fresnel principle. These characteristic behaviors are exhibited when a wave encounters an obstacle or a slit that is comparable in size to its wavelength. Similar effects occur when a light wave travels through a medium with a variable refractive index, or when a sound wave travels through a medium with variable acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, X-rays, and radio waves.
Since physical objects have wave properties (at the atomic level), diffraction also occurs with matter and can be studied according to the principles of quantum mechanics. The Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1660.
While diffraction occurs when propagation waves encounter such changes, their effects are generally more pronounced for waves whose wavelength is approximately comparable to the object's dimensions or diffraction slit. If the obstructing object provides multiple closely spaced openings, a complex pattern of varying intensity may result. This is due to the addition or interference of different parts of a wave traveling to the observer by different paths, where different path lengths result in different phases (see diffraction grid and wave overlap). The diffraction formalism can also describe the way in which finite extension waves propagate in free space. For example, the expansion profile of a laser beam, the beam shape of a radar antenna and the field of view of an ultrasonic transducer can be analyzed using diffraction equations.
Since physical objects have wave properties (at the atomic level), diffraction also occurs with matter and can be studied according to the principles of quantum mechanics. The Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1660.
While diffraction occurs when propagation waves encounter such changes, their effects are generally more pronounced for waves whose wavelength is approximately comparable to the object's dimensions or diffraction slit. If the obstructing object provides multiple closely spaced openings, a complex pattern of varying intensity may result. This is due to the addition or interference of different parts of a wave traveling to the observer by different paths, where different path lengths result in different phases (see diffraction grid and wave overlap). The diffraction formalism can also describe the way in which finite extension waves propagate in free space. For example, the expansion profile of a laser beam, the beam shape of a radar antenna and the field of view of an ultrasonic transducer can be analyzed using diffraction equations.