Thus, specifying the cross section for a given reaction is a proxy for stating the probability that a given scattering process will occur. The probability for any given reaction to occur is in proportion to its cross section. Scattering cross sections may be defined in nuclear, atomic, and particle physics for collisions of accelerated beams of one type of particle with targets (either stationary or moving) of a second type of particle.
![rhinoceros 6 cut a cross section rhinoceros 6 cut a cross section](https://www.dlubal.com/-/media/Images/website/components/photogalleries/solutions/anwendungsbereiche/bim-orientierte-planung/rhinoceros-grasshopper/03-en.png)
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 with integral calculus, we can find the total cross section. When a cross section is integrated over all scattering angles (and possibly other variables), it is called a total cross section or integrated total cross section. When a cross section is specified as the differential limit of a function of some final-state variable, such as particle angle or energy, it is called a differential cross section (see detailed discussion below). If the particles interact through some action-at-a-distance force, such as electromagnetism or gravity, their scattering cross section is generally larger than their geometric size. If the particles are hard inelastic spheres that interact only upon contact, their scattering cross section is related to their geometric size. When two discrete particles interact in classical physics, their mutual cross section is the area transverse to their relative motion within which they must meet in order to scatter from each other. For example, plasmonic nanoparticles can have light scattering cross sections for particular frequencies that are much larger than their actual cross-sectional areas. It is not uncommon for the actual cross-sectional area of a scattering object to be much larger or smaller than the cross section relative to some physical process. It is important to note that although the cross section has the same units as area, the cross section may not necessarily correspond to the actual physical size of the target given by other forms of measurement. In classical physics, this probability often converges to a deterministic proportion of excitation energy involved in the process, so that, for example, with light scattering off of a particle, the cross section specifies the amount of optical power scattered from light of a given irradiance (power per area). In a way, it can be thought of as the size of the object that the excitation must hit in order for the process to occur, but more exactly, it is a parameter of a stochastic process. Cross section is typically denoted σ ( sigma) and is expressed in units of area, more specific in barns. For example, the Rutherford cross-section is a measure of probability that an alpha particle will be deflected by a given angle during a collision with an atomic nucleus. a particle beam, sound wave, light, or an X-ray) intersects a localized phenomenon (e.g.
![rhinoceros 6 cut a cross section rhinoceros 6 cut a cross section](https://i.natgeofe.com/n/dd79c52d-28e0-4930-b575-661047d21987/NationalGeographic_2451025_2x1.jpg)
In physics, the cross section is a measure of the probability that a specific process will take place when some kind of radiant excitation (e.g.
![rhinoceros 6 cut a cross section rhinoceros 6 cut a cross section](https://simplyrhino.co.uk/images/support/nvidia/quadro-card-test-truck.jpeg)
It is not to be confused with Radar scattering cross section. "Scattering cross section" redirects here.