Editing Forward scatter (section)

== General description ==
Whenever waves encounter obstacles of any type there are changes in the direction of the waves ([[wave vector]]) by diffraction,<ref name=":0">{{Cite book |last=Cowley |first=J. M. |title=Diffraction physics |date=1995 |publisher=Elsevier Science B.V |isbn=978-0-444-82218-5 |edition=3rd |series=North-Holland personal library |location=Amsterdam ; New York}}</ref><ref>{{Cite book |last=Born |first=Max |title=[[Principles of optics]]: electromagnetic theory of propagation, interference and diffraction of light |last2=Wolf |first2=Emil |date=2017 |publisher=Cambridge University Press |others=Avadh B. Bhatia |isbn=978-0-521-64222-4 |edition=Seventh (expanded) edition, 13th printing |location=Cambridge}}</ref> and sometimes its energy by [[inelastic scattering]]. These processes occur for all types of waves, although how they behave varies with both their type and that of the obstacle. As illustrated in the figure, if the change in the wave vector '''q''' is fairly small the scattered wave moves in close to the same direction as the input—it has been scattered. In most cases the change in the wave vector scales inversely with the size of obstacles, so forward scattering is more common when the obstacles are large compared to the [[wavelength]] of the radiation.
[[File:Wave_diffraction_at_the_Blue_Lagoon,_Abereiddy.jpg|thumb|Wave diffraction at the Blue Lagoon, Abereiddy]]
In many cases the waves of interest have relatively small wavelengths, for instance high-energy electrons<ref name=":0" /> or [[X-ray]]s.<ref>{{Cite book |last=Warren |first=B. E. |url=https://www.google.com/books/edition/X_ray_Diffraction/wfLBhAbEYAsC?hl=en |title=X-ray diffraction |date=1990 |publisher=Dover Publications |isbn=978-0-486-66317-3 |edition= |location=New York}}</ref> However, the process is very general and can also be seen when water flows through a narrow channel as shown in the figure at the Blue Lagoon.