Radiant and Luminous Flux

　　Radiant and Luminous Flux

　　光源的辐射通量随光源和波长而变化。理解变化是照明设计的关键

　　物理学家研究系统辐射电磁能量会使用测量仪器，在平时的MKS单位能量。由系统发出的能量，你将获得焦耳。辐射能、辐射通量P的生产时间率将被定义为：

　　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，