![]() Fraunhofer pattern is easier to observe practically by a spectrometer. The diffracted rays which are parallel to one another are brought to focus with the help of a convex lens. ![]() Hence in this case the wavefront undergoing diffraction is plane. In the Fraunhofer diffraction, the source and the screen are at infinite distances from the obstacle producing diffraction. In such a case the wave front undergoing diffraction is either spherical or cylindrical. In one approximation, the viewing position is assumed to be far from the obstruction the resulting diffraction is called Fraunhofer diffraction. In the Fresnel diffraction, the source and the screen are at finite distances from the obstacle producing diffraction. (i) Fresnel diffraction and (ii) Fraunhofer diffraction. A series of coloured images are observed.ĭiffraction phenomenon can be classified under two groups 6.6: Fresnel and Fraunhofer Approximations. In practice, diffraction of light can be observed by looking at a source of white light through a fine piece of cloth. As the wavelength of light is very small, compared to that of sound wave and even tiny obstacles have large size, compared to the wavelength of light waves, diffraction effects of light are very small. Since the sound waves have a greater wavelength, the diffraction effects are pronounced. The waves are diffracted, only when the size of the obstacle is comparable to the wavelength of the wave.įresnel showed that the amount of bending produced at an obstacle depends upon the wavelength of the incident wave. Diffraction is a characteristic property of waves. This bending of waves around the edges of an obstacle is called diffraction. Similarly, waves on the surface of water also bend round the edges of an obstacle and spread into the region behind it. Sound produced in an adjoining room reaches us after bending round the edges of the walls. Sound is propagated in the form of waves.
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