User:Wsetzer/sandbox
From Wikipedia, the free encyclopedia
In physics, a cross section is an effective area that governs the probability of an event or reaction. The term is derived from the purely classical picture of (a large number of) point-like projectiles directed onto a target area that includes a solid target. Assuming that an event will occur if the projectile hits the solid target, and will not occur if it misses, the total event probability for the single projectile will be the ratio of the area of the section of the solid (the cross section, represented by
) to the total targeted area. This basic concept is then extended to the cases where the reaction probability in the targeted area assumes intermediate values - because the target itself is not homogeneous, or because the interaction is mediated by a non-uniform field. scattering events which are commonly described by cross sections.