An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of over a specific portion of the, typically used in to identify materials. The variable measured is most often the of the light but could also, for instance, be the state. The independent variable is usually the of. (often simply called "spectrometers"), in particular, show the intensity of as a function of wavelength or of frequency. The different wavelengths of light are separated by in a or by by a. is an example. These spectrometers utilize the phenomenon of. The light from a s.