We can use this equation to calculate the diffraction pattern that is created by the waves that are passing through an aperture or around an object if we are viewing it from relatively close proximity to the object. It is an approximation of the Kirchhoff-Fresnel diffraction. Therefore, it is also named near-field diffraction. What is Fresnel Diffraction?įresnel diffraction is an equation we can apply to the propagation of waves in the near field. This phenomenon is named far-field, and we can use the Fraunhofer diffraction equation to model this type of diffraction. Therefore, the propagation path for a wavelet can be considered as parallel from each and every point of the aperture to the point of observation. If we are going to determine the diffraction that occurs when there is a distance between the aperture and the plane of observation, the optical path lengths between the aperture and the point of observation can differ much less than the wavelength of the light. the addition of two waves with equal amplitude (which are in phase) can result in a displacement having a doubled amplitude. This addition of wavelets includes many waves of varying phases and amplitudes. We can model the effects of diffraction using the Huygens-Fresnel principle, where Huygens postulated that the points on a primary wavefront could act as a source of spherical secondary wavelets, and we can use the sum of these secondary wavelets to determine the form of the wave that is proceeding at any subsequent time. This equation was named after the scientist Joseph Von Fraunhofer. Moreover, we can use this equation for modelling the diffraction of waves when the diffraction pattern appears at the focal plane of an imaging lens. Summary What is Fraunhofer Diffraction?įraunhofer diffraction is an equation that is useful in modelling the diffraction of waves where the diffraction pattern appears at a long distance from the diffracting object. Fraunhofer vs Fresnel Diffraction in Tabular Formĥ. The key difference between Fraunhofer and Fresnel diffraction is that Fraunhofer diffraction equation involves the modelling of the diffraction of waves having a diffraction pattern appearing at a long distance from the diffracting object, whereas Fresnel diffraction equation involves the same modelling method for diffraction pattern created near the object.ĭiffraction is a phenomenon that can be described as the scattering of light around an object when a light beam is partly blocked by that object where we can see dark and light bands at the edge of the shadow of that object.Ĥ.
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