Kiirgusvoo

Kiirgusvoo, or radiant flux, is a radiometric quantity that describes the total power carried by electromagnetic radiation. It is the rate at which radiant energy is transferred, emitted, or received, summed over all directions and wavelengths. The SI unit is the watt (W), and kiirgusvoo represents the aggregate energy flow of a radiation field.

In radiometry, kiirgusvoo is denoted Φe and can be described as the integral of radiant power over a source or surface. If a source emits into all directions (approximately 4π steradians), kiirgusvoo equals the total emitted power. For a surface radiating energy, the total flux leaving the surface is the radiant exitance (emittance) M multiplied by the area A, Φ = ∫∫ M dA. In spectral form, one can use Φe,λ to denote the flux per wavelength and integrate over wavelengths.

Kiirgusvoo is distinct from related quantities such as radiant intensity I (power per unit solid angle, W/sr), irradiance E (power per unit area incident on a surface, W/m^2), and radiant exitance M (power per unit area emitted by a surface, W/m^2). Radiant flux provides a global measure of energy transfer, while the other quantities describe its distribution in direction or over surfaces.

Measurement and applications: kiirgusvoo is measured with radiometers or integrating spheres and is used in lighting engineering to quantify total emission, as well as in radiative heat transfer calculations in engineering, astronomy, and remote sensing. The concept applies across infrared, visible, and other spectral regions.

See also: Radiant intensity, Radiance, Radiant exitance, Luminous flux.