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建筑环境学chapterthermalcomfortable Illuminance 照度 Illuminance is the density of luminous flux reaching a surface Unit : lux (lx) 1lx=1lumen/(meter)2 If light is falling a surface at right angles to the surface 提示：照度可直接相加，几个光源同时照射被照面时，其上的照度为单个光源分别存在时的照度的代数和。 照度 单位面积被照面上的光通量 定义式 单位I 等于1lm的光通量均匀分布在1m2被照面上 表示被照面上的光通量密度 * Illuminance 照度 in several different cases Inverse square law of illumination 照度的平方反比定律 The llluminance produced by a point source of light decreases in inverse proportion to the square of the distance from the source. Worked example 6.2 A lamp has a luminous intensity of 1200cd and acts as a point source. Calculate the illuminance produced on surfaces at the following positions a) At 2m distance from the lamp, and b) At 6m distance from the lamp Know: I=1200cd d1=2m and d2=6m, E=?