A spectrophotometer is an instrument which is used to measure the intensity of electromagnetic radiation at different wavelengths. Important features of spectrophotometers are spectral band with and the range of absorption or reflectance measurement.pectrophotometry is a quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. It is more specific than the common term electromagnetic spectroscopy which deals with visible light near ultraviolet and near infra-red.