Obviously, it is important to choose your words carefully, especially when both professionals and laypeople are present. A solid angle is the ratio of the sphere surface area enclosed to the square of the radius. Luminous Energy is visually evaluated radiant energy traveling in the form of electromagnetic waves. Luminous flux is the time rate of flow of luminous energy. For example, the light emitted from a 34 Watt fluorescent lamp is typically at a rate of 2850 lumens.
Luminous intensity is the solid-angular luminous flux density in a given direction.
It indicates the ability of a light source to produce illumination in a given direction. Relationships among candela, lumen, footcandle and lux. Though their meanings are vastly different, the two terms sound nearly indistinguishable in rapid speach. Since then And since, from the definition of solid angle, then Thus the illuminance at a point is inversely proportional to the square of the distance between the light source and the point. The application of the ISL is discussed in the calculation section .