 Radiative flux

Radiative flux is the first angular moment $F_{\nu }=\int I_{\nu }\cos \theta ,d\Omega$ and measures net radiant power crossing unit area.

Radiative flux, often referred to as radiant flux, is a measure of the amount of radiant energy (such as light or thermal radiation) that passes through a given surface area per unit time. It is typically expressed in watts (W), where one watt equals one joule of energy per second.