Matter has its own original nature, and it can distinguish different substances by property. Due to the different composition of the material, under certain conditions, the substance can emit the light harmonic of its characteristics. We use the properties of the spectrum to determine the composition of the matter.
Light has a wave character, so the wavelength of light is a symbol of it. The light of different colors shows that its wavelength is different. From the ultraviolet light of the short wave to the infrared light of the long wave, all the visible light is visible. A series of light wavelengths arranged in separate wavelengths form the so-called spectrum. The spectral range of emission spectrum analysis is only a part of ultraviolet field. It is part of visible and infrared domain. The wavelength is from 1600~8500A (the wavelength of light is used to measure A or 1A=10-5cm=10-7mm=0.1nm).