A UV spectrometer works by passing light from the ultraviolet (UV) spectrum through a sample and measuring the amount of light that is absorbed or transmitted at different wavelengths. The instrument consists of a light source, a monochromator (to select specific wavelengths), a cuvette holder, and a detector. The detector measures the intensity of the light that passes through the sample, and the data is used to create a spectrum showing the absorbance or transmittance as a function of wavelength.