Spectrophotometer

n.	1.	(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.

Noun

1.

spectrophotometer - a photometer for comparing two light radiations wavelength by wavelength

photometer