electromagnetic energy per unit time, area, solid area and spectral band, i.e., electromagnetic energy radiating in a given direction

A measure of the energy radiated by the object together with the frequency distribution of that radiation.

The quantity of energy delivered to and striking a surface or object per unit of time, measured in wafts.

The flux density of radiant energy per unit solid angle and per unit area. Watts per square meter per steradian. (W/m2/str).

A measure, in power units, of the total radiant flux from a surface, in a given direction.

The radiant flux as Watts per unit soled angle per unit of projected area of the source in units described as watts/m2/steradian.

Brightness; the radiant power per unit solid angle and per unit area of a radiating surface.

the amount of electromagnetic radiation leaving or arriving at a point on a surface

Output measurement for a point source; measured in: power per unit area per solid area defined by the unit watt/square meter-steradian.

Emittance, steradiancy; the rate of radiant energy emission per unit solid angle per unit of projected area of a source in a stated angular direction from the surface per wavelength; for example, in units, watts per square meter per solid angle per wavelength (W/M2/steradian/ nm).

Radiance is the power of EM radiation incident on unit area per unit solid angle in a given direction.

Radiance is a measure of radiometric flux density per unit solid angle. Radiance is typically expressed in W/cm/sr (watts per square centimeter per steradian).

The radiation energy per unit time coming from a specific direction and passing through a unit area perpendicular to the direction.

The total intensity of thermal energy (radiant flux) which can be observed from a surface. It is scaled by unit of solid angle of view and by unit of area from the surface. The flux includes all forms of radiation emission, reflection and transmission.

a measure of the intensity of the radiant energy flux emitted by a body in a given direction

In radiometry, a measure of the intrinsic radiant intensity emitted by a radiator in a given direction.

Reflected light or emitted radiation at a particular wavelength and in a particular direction. Cloud radiance is either reflected sunlight in visible and near-infrared wavelengths or emitted radiation in infrared wavelengths.

The amount of light energy or photons measured in a specified time period in a unit area from a given direction.

A measure of radiant intensity produced by a material in a given direction and per unit wavelength interval, denoted by Il = dQ/dt/dA/dl/dW and measured in MKS units as Watts/m2/steradian/micron. Can also be defined as the radiant flux per unit solid angle and wavelength interval.

Measure of the energy radiated by an object. In general, radiance is a function of viewing angle and spectral wavelength and is expressed as energy per solid angle.

The radiant flux emitted by a light source per unit solid angle and per unit projected area of radiating surface (expressed in watts per steradian per surface unit).

A radiometric term for the rate at which radiant energy in a set of directions confined to a unit solid angle around a particular direction is transferred across unit area of a surface (real or imaginary) projected onto this direction. Unlike irradiance, radiance is a property solely of a radiation field, not of the orientation of the surface. The SI units of radiance are W mâˆ’2 srâˆ’1. In general, radiance depends on time, position, and direction as well as frequency ( monochromatic or spectral radiance) or range of frequencies. Irradiance for any surface is the integral of radiance over a hemisphere of directions above or below that surface. The photometric equivalent of radiance is luminance, obtained by integrating spectral radiance weighted by luminous efficiency over the visible spectrum.

Radiance and spectral radiance are radiometric measures that describe the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle in a specified direction. They are used to characterize both emission from diffuse sources and reflection from diffuse surfaces. The SI unit of radiance is watts per steradian per square metre (WÂ·sr-1Â·m-2).