(Opt.) An instrument for measuring or comparing the intensities of the colors of the spectrum.
2.
(Chem., Physics) An analytical instrument for measuring the degree of absorption of light at different wavelengths by a chemical substance. A specific pattern of absorption intensities at a series of wavelengths is a characteristic of each different chemical substance.
... the stratosphere, speeding eastward, the immense mass of the Boise slowed abruptly, although no projector had slackened its effort. Cleveland, eyes upon interferometer grating and spectrophotometer charts, fingers flying over calculator keys, grinned ... — Triplanetary • Edward Elmer Smith