The main components include the light source, monochromator, sample holder, detector, and the output system, all of which work together to measure light across various wavelengths. While component types and devices vary from brand to brand, the core principle of how a spectrophotometer works stays largely the same. Listed below are some of the key components that make measuring transmittance possible. Figure 1: Components of a spectrophotometer: Light emitted from the source. Internal structure of a grating spectrometer: Light comes from left side and diffracts on the upper middle reflective grating. It typically emits light across a. Two kinds of lamps, a Deuterium for measurement in the ultraviolet range and a tungsten lamp for measurement in the visible and near-infrared ranges, are used as the light sources of a spectrophotometer.