Forward scattering is the deflection of waves by small angles so that the continue to move in close to the same direction as they started with. It can occur with all types of waves, for instance light, ultraviolet radiation, X-rays as well as matter waves such as electrons, neutron and even water waves. It can be due to diffraction, refraction, and low angle reflection. It almost always occurs when the wavelength of the radiation used is small relative to the features which lead to the scattering. Forward scatter is essentially the reverse of backscatter.
Many different examples exist, and there are very large fields where forward scattering dominates, in particular for electron diffraction and electron microscopy, X-ray diffraction and neutron diffraction. In these the relevant waves are transmitted through the samples. One case where there is forward scattering in a reflection geometry is reflection high-energy electron diffraction.
Forward scattering can make a back-lit comet appear significantly brighter because the dust and ice crystals are reflecting and enhancing the apparent brightness of the comet by scattering that light towards the observer.[1] Comets studied forward-scattering in visible-thermal photometry include C/1927 X1 (Skjellerup–Maristany), C/1975 V1 (West), and C/1980 Y1 (Bradfield).[2] Comets studied forward-scattering in SOHO non-thermal C3 coronograph photometry include 96P/Machholz and C/2004 F4 (Bradfield).[2] The brightness of the great comets C/2006 P1 (McNaught) and Comet Skjellerup–Maristany near perihelion were enhanced by forward scattering.[3]
This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22.