ما معنى كل من: cross section ؟

[الربيعي]

scattering cross section , absorption cross section and cross section

[رجب مصطفى]

Cross Section

In studying nuclear reactions and other collision processes, we are always interested in a quantitative measure the probability with which the collision process occurs. This quantitative measure is always expressed through a parameter called cross-section

The concept of a cross section is used to express the likelihood of interaction between particles. When particles are thrown against a foil made of a certain substance, the cross section is a hypothetical area measure around the target particles (usually its atoms) that represents a surface. If a particle of the beam crosses this surface, there will be some kind of interaction

The term is derived from the purely classical picture of (a large number of) point-like projectiles directed to an area that includes a solid target. Assuming that an interaction will occur (with 100% probability) if the projectile hits the solid, and not at all (0% probability) if it misses, the total interaction probability for the single projectile will be the ratio of the area of the section of the solid (the cross section, represented by σ) to the total targeted area

The concept of cross section, as its name suggests, is that of effective area for collision

هذا بصفة عامة ... فإذا كانت التفاعل الحادث هو إستطارة مثلاً ... سمي المقطع الرضي للإستطارة، وإذا كان التفاعل هو إمتصاص ... سُمي بـ المقطع العرضي للإمتصاص ...

Scattering cross-section, σscat, relates the scattering of light or other radiation to the number of particles present. In terms of area, the total cross-section (σ) is the sum of the cross-sections due to absorption, scattering and luminescence: σ = σA + σS + σL

Absorption cross section is a measure for the probability of an absorption process

More generally, the term cross section is used in physics to quantify the probability of a certain particle-particle interaction, e.g., scattering, photoabsorption, etc

وعموماً ... المقطع العرضي هو عبارة عن المساحة (السطح) المحيطة بالهدف، إذا مرت الحزمة (جسيم أو شعاع) خلالها فمن الممكن أو المحتمل أن يحدث التفاعل.

والشكل التالي ... يوضح أو يبين معنى المقطع العرضي التفاضلي differential cross-section أو dσ/dΩ .

دمتم في رعاية الله وحفظه

[الربيعي]

اخي الكريم رجب شكرآ جزيلآ لك ..جزاك الله كل خير