collisional cross section
sekanj-e oskarmand-e hamkubeši
Fr.: section efficace de collision
Same as → cross section.
Fr.: 1) section plane; 2) section efficace
1) Math: The intersection of a plane with a geometric figure,
usually at right angles to an axis of symmetry.
In classical mechanics, the cross section for the collision of a point particle with a hard sphere is just be the surface of a section through the middle of the sphere. This explains the name "cross section." → cross; → section.
Thomson cross section
Fr.: section efficace de Thomson
The → cross section involved the → Thomson scattering of electromagnetic waves by a free electron. It is defined by: σT = 8πre2/3, where re is the classical → electron radius. Its value is 0.665 245 x 10-28 m2.