User:Epzcaw/Diffraction (optics)





Diffraction is defined in the Penguin Dictionary of Science as the effect which occurs when a beam of light passes through an aperture or past the edge of an opaque obstacle, where patterns of light and dark bands are observed in the light beam extending into the shadow and is a particular case of interference (optics)". Richard Feynman says that "no-one has ever been able to define the difference between interference and diffraction satisfactorily. It is just a question of usage, and there is no specific, important physical difference between them." He suggests that when there are only a few sources, say two, we call it interference, as in Young's slits, but with a large number of sources, the process is labelled diffraction.

Sommerfeld, who made major contributions to the theory of diffraction, defined it as "any deivation of light rays from rectilinear paths whihc cannot be explained by reflection or refraction".

=Diffraction in the development of the theory of light propagation=

Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665.

Discuss Huygens, Fresnel, Kirchoff, Sommerfeld in general terms.

The propagation of electromagnetic waves is predicted by solving Maxwell's equations for an isotropic medium where there are no sources of electric or magnetic charges. The waves have varying electric and magnetic fields which are orthogonal to one another, and also to the direction of propagation of the waves. Waves whose frequency lies between 4-8.1014 Hz form the visible spectrum, i.e they are light waves.

Examples
Appropriate images

Models of diffraction
Need to point out that these are all scalar but work well nonetheless.