Diffraction refers to various phenomena that occur when a wave encounters an obstacle or opening. It is defined as the bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word diffraction and was the first to record accurate observations of the phenomenon in 1660. Infinitely many points (three shown) along length d project phase contributions from the wave front, producing a continuously varying intensity θ on the registering plate. In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wave front as a collection of individual spherical wavelets. The characteristic bending pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image. This is due to the addition, or interference, of different points on the wave front (or, equivalently, each wavelet) that travel by paths of different lengths to the registering surface. If there are multiple, closely spaced openings a complex pattern of varying intensity can result.

Rumina Shams

24 resources

1

1

0

Like