Radiant and Luminous Flux

　　光源的輻射通量隨光源和波長而變化。理解變化是照明設計的關鍵

　　物理學家研究系統(tǒng)輻射電磁能量會使用測量儀器，在平時的MKS單位能量。由系統(tǒng)發(fā)出的能量，你將獲得焦耳。輻射能、輻射通量P的生產(chǎn)時間率將被定義為：

　　where t is time. The MKS unit of radiant flux would be， therefore， joules per second or watts.

　　Generally， the radiant flux from a source differs for different wavelengths. The flux at a given wavelength， λ， and in a spectral interval dλ is given by Pλdλ。 A plot of Pλ versus λ gives the power spectrum of the radiator. Power spectra may be either continuous or discrete. The usual tungsten filament lamp has a continuous power spectrum like that of Figure 1. The mercury lamp spectrum shown in Figure 2 is a typical line spectrum with the spectral lines corresponding to energy level transitions. Fluorescent lamps have discrete spectra superimposed on a continuous spectra. The total radiant flux P emitted by a light source is the integral of Pλdλ over all wavelengths，