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Forward scattering is the deflection of waves by small angles so that they continue to move in close to the same direction as before the scattering. It can occur with all types of waves, for instance light , ultraviolet radiation, X-rays as well as matter waves such as electrons , neutrons and even water waves .
in astronomy, backscattered light is that which is reflected with a phase angle of less than 90°. In other cases, the scattering intensity is enhanced in backward direction. This can have different reasons: In alpenglow, red light prevails because the blue part of the spectrum is depleted by Rayleigh scattering.
Wine glass in LCD projectors light beam makes the beam scatter.. In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiation) in the medium through which they pass.
The equation was later extended to quantum scattering theory by several individuals, and came to be known as the Bohr–Peierls–Placzek relation after a 1939 paper. It was first referred to as the "optical theorem" in print in 1955 by Hans Bethe and Frederic de Hoffmann , after it had been known as a "well known theorem of optics" for some time.
Multiple-scattering effects of light scattering by particles are treated by radiative transfer techniques (see, e.g. atmospheric radiative transfer codes). The relative size of a scattering particle is defined by its size parameter x, which is the ratio of its characteristic dimension to its wavelength:
This is one of the most robust interference phenomena that survives multiple scattering, and it is regarded as an aspect of a quantum mechanical phenomenon known as weak localization (Akkermans et al. 1986). In weak localization, interference of the direct and reverse paths leads to a net reduction of light transport in the forward direction.
For example, in Rayleigh scattering, the intensity scattered at the forward and backward angles is greater than the intensity scattered sideways, so the forward differential scattering cross section is greater than the perpendicular differential cross section, and by adding all of the infinitesimal cross sections over the whole range of angles ...
The apparent change in direction of a light ray as it enters a sheet of glass at angle can be understood by the Huygens construction. Each point on the surface of the glass gives a secondary wavelet. These wavelets propagate at a slower velocity in the glass, making less forward progress than their counterparts in air.