Candela of a single point light source of intensity "I", at a distance "r" and normally incident, this reduces to Candela The candela ( or ; symbol: cd) is the base unit of luminous intensity in the International System of Units (SI); that is, luminous power per unit solid angle emitted by a point light source in a particular direction. Luminous intensity is analogous to radiant intensity, but instead of simply adding up the contributions of every wavelength of light in the source's spectrum, the contribution of each wavelength is weighted by the standard luminosity function (a model of the sensitivity
Banach measure Banach measure In mathematics, Banach measure in measure theory may mean a real-valued function on an algebra of all subsets of a set (for example, all subsets of the plane), by means of which a rigid, finitely additive area can be defined for every set, even when a set does not have a true geometric area. That is, this is a type of generalized measure getting around the phenomenon of non-measurable sets. However, as the Vitali set shows, it cannot be countably additive. A Banach measure on a set Ω is a finite measure μ ≠ 0 on P(Ω), the