rtain range of wavelength . Spectrophotometry. A spectrophotometer is an analytical instrument used to quantitatively measure the transmission or reflection of visible light, UV light or infrared light. ... Spectrophotometers are widely used in various disciplines such as physics, molecular biology, chemistry and biochemistry.Spectrophotometry. Spectrophotometry is a method to measure how much a chemical substance absorbs light by measuring the intensity of light as a beam of light passes through sample solution. The basic principle is that each compound absorbs or transmits light over a certain range of wavelength.The spectrophotometer works by passing a light beam through a sample to measure the light intensity of a sample. These instruments are used in the process of measuring color and used for monitoring color accuracy throughout production. They are primarily used by researchers and manufacturers everywhere.There are two basic types of atomic spectrometers: emission and absorbance. In either case a flame burns the sample, breaking it down into atoms or ions of the elements present in the sample. An emission instrument detects the wavelengths of light released by the ionized atoms.