Avogadro constant Avogadro constant In chemistry and physics, the Avogadro constant, named after scientist Amedeo Avogadro, is the number of constituent particles, usually atoms or molecules, that are contained in the amount of substance given by one mole. Thus, it is the proportionality factor that relates the molar mass of a substance to the mass of a sample. The Avogadro constant, often designated with the symbol "N" or "L", has the value in the International System of Units (SI). (The parentheses there represent the degree of uncertainty.) Previous definitions of chemical quantity involved the Avogadro number, a historical term closely related to
Intensity (physics) irradiance, depending on the background of the person using the term. Radiance is also sometimes called "intensity", especially by astronomers and astrophysicists, and in heat transfer. Intensity (physics) In physics, intensity is the power transferred per unit area, where the area is measured on the plane perpendicular to the direction of propagation of the energy. In the SI system, it has units watts per square metre (W/m). It is used most frequently with waves (e.g. sound or light), in which case the "average" power transfer over one period of the wave is used. "Intensity" can be applied to other circumstances