🌐EnglishEnglishEspañolItalianoРусскийالعربية中文日本語EntityQ1967557· pop 6· linked from 268 articlesspectral power distributionpower per unit area per unit wavelength of a wavelength concentration, important for a substance's transmittance, reflectivity, and absorbanceConnectionslightingEntityilluminanceEntityCategoriesColorLightingPhysical quantitiesRadiometry