spectrophotometry

See spectrophotometric.

* * *

Branch of spectroscopy dealing with measurement of radiant energy transmitted or reflected by a body as a function of wavelength.

The measurement is usually compared to that transmitted or reflected by a system that serves as a standard. In chemistry and physics, different types of spectrophotometers cover wide ranges of the electromagnetic spectrum: ultraviolet (UV), visible light, infrared (IR), or microwave. UV spectrophotometry is particularly useful in detecting and quantifying colourless substances in solution. IR spectrophotometry is used mostly to study the molecular structures of complex organic compounds. In astronomy and astrophysics, spectrophotometric studies also include the X-ray and gamma ray ranges of the spectrum. See also colorimetry.

* * *

▪ physics

 branch of spectroscopy that deals with measurement of the radiant energy transmitted or reflected by a body as a function of the wavelength. Ordinarily the intensity of the energy transmitted is compared to that transmitted by some other system that serves as a standard. Different types of modern spectrophotometers cover wide ranges of the electromagnetic spectrum: X-ray, ultraviolet, visible, infrared, or microwave.

      Two laws express the relationship between the absorption of radiant energy and the absorbing medium. According to Bouguer's (or Lambert's) law, each layer of equal thickness of the medium absorbs an equal fraction of the energy traversing it. According to Beer's law, the absorptive capacity of a dissolved substance is directly proportional to its concentration in a solution.

      Ultraviolet spectrophotometry is particularly useful in detecting colourless substances in solution and measuring their concentration. Infrared spectrophotometry is most commonly used in studying the molecular structures of complex organic compounds.

* * *