intensity

In physics, intensity is a measure of the time-averaged energy flux. To find the intensity, take the energy density (that is, the energy per unit volume) and multiply it by the velocity at which the energy is moving. The resulting vector has the units of power divided by area (i.e. watt/m²). It is possible to define the intensity of the water coming from a garden sprinkler, but intensity is used most frequently with waves (i.e. sound or light).
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(n.)
The state or quality of being intense; intenseness; extreme degree; as, intensity of heat, cold, mental application, passion, etc.
  

(n.)
The magnitude of a distributed force, as pressure, stress, weight, etc., per unit of surface, or of volume, as the case may be; as, the measure of the intensity of a total stress of forty pounds which is distributed uniformly over a surface of four square inches area is ten pounds per square inch.
  

(n.)
The degree or depth of shade in a picture.
  

(n.)
The amount or degree of energy with which a force operates or a cause acts; effectiveness, as estimated by results produced.
  

The square of the electric field strength of an electromagnetic wave. Note: Intensity is proportional to irradiance and may be used in place of the term "irradiance" when only relative values are important.

(P,I) Energy of radiation striking a unit area per unit time. The SI unit of radiant power is J m-2 s-1.