A spectrometer works kind of like a telescope, but it is going to look at the wave nature of light. A light beam comes in the spectrometer and is broken up to allow narrow wavelengths of light to enter. The light appears white if all the wavelenghts are visible. When the light is directed at something, some color is absorbed and and white light will be colored as it is missing some of the wavelenghts of the white light. So, the spectrometer works by measuring masses and how they absorb light.