太阳光是一种能对人眼视觉神经起刺激作用的电磁辐射。根据光的波长范围分为可见光光谱(380nm～780nm)、紫外光辐射(<380nm)、红外辐射(>780nm)。紫外光辐射波长比可见光波长短,人眼是看不见的。科学家又将其分为短波或极短波紫外线(<290nm)、中波或远波紫外线(290nm<320nm)长波或近波紫外线(<320nm)波长越短,对人体及其他物体的危害越大。 Sunlight is a type of electromagnetic radiation that stimulates the human visual cortex. According to the light wavelength range is divided into visible light spectrum (380nm ~ 780nm), ultraviolet radiation (<380nm), infrared radiation (> 780nm). UV radiation wavelength shorter than visible light, the human eye is invisible. Scientists then classify them into shortwave or very shortwave ultraviolet (<290nm) and shorter wavelengths of mediumwave or farwave (290nm <320nm) or nearwave ultraviolet (<320nm), which are more harmful to humans and other objects.