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. An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument. 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. By analyzing how much light is absorbed at specific wavelengths, we can learn. Optical spectroscopy is a technique that is used to measure light intensity in the ultraviolet (UV), visible (VIS), near-infrared (NIR), and infrared (IR) range of the electromagnetic spectrum.
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