- An instrument for measuring the intensity of radiant energy of desired frequencies absorbed by atoms of molecules. Substances are analyzed by converting the absorbed energy to electrical signals, proportional to the intensity of radiation.
- An instrument which measures the intensity of radiation as a function of wavelength. Such instruments usually analyze visible light, in which case they incorporate a photometer, but may also be designed to assess other intervals of the electromagnetic spectrum, such as the infrared, microwave, or X-ray regions. A spectrophotometer may be utilized to quantify absorption, emission, reflectance, transmittance, absorptance, and so on. Also called spectroradiometer.
- noun an instrument used to measure colour by giving a wavelength-by-wavelength analysis of the light reflected from the surface