Imagine someone standing in the sunlight on a sunny day. The sunlight they feel on their skin is carrying energy. The amount of this energy hitting each square meter of their skin every second is the radiant flux.
Formula
Units
Where: – S (λ) is the spectral power distribution, which tells us how much power is being carried by light at each wavelength (λ). – λ1 and λ2 define the wavelength range of the radiation of interest. For example, to know the radiant flux of visible light, one must integrate over wavelengths from about 400 nm (blue) to 700 nm (red). 1 W = 1 J/s It means that if a source emits or receives one joule of radiant energy every second, its radiant flux would be equivalent to one watt. The watt is often used to quantify the power output of devices such as light bulbs and lasers. When higher levels of radiant flux are involved, kilowatts (kW) or even megawatts (MW) may be used.
