a diagram of the light path through a visible-light spectrophotometer is shown to the right a beam of light emerges from its source and passes through a prism which dissects the light into a continuous spectrum of wavelengths the user can select which single specific wavelength of light passes to the sample with the monochromator light of a single wavelength is called monochromatic light the monochromatic light that passes to the sample is the known as incident light its intensity is represented the value. as the incident light passes through the sample a certain amount of the light will be absorbed by the sample the monochromatic light that is not absorbed emerges from the sample it is called transmitted and its intensity is represented by the value l the intensity of the transmitted might is detected by a photodetector