In physics,<unk>  is the quantitative study of electromagnetic spectra. It is more specific than the general term electromagnetic spectroscopy in that<unk>  deals with visible light, near-ultraviolet, and near-infrared.   Also, the term does not cover time-resolved spectroscopic techniques.<unk>  involves the use of a spectrophotometer. A spectrophotometer is a photometer (a device for measuring light intensity) that can measure intensity as a function of the color, or  more specifically, the wavelength of light. There are many kinds of spectrophotometers. Among the most important distinctions used to classify them are the wavelengths they work with, the measurement techniques they use, how they acquire a spectrum, and the sources of intensity variation they are designed to measure. Other important features of spectrophotometers include the spectral bandwidth and linear range.
Perhaps the most common application of spectrophotometers is the measurement of light absorption, but they can be designed to measure diffuse or specular reflectance. Strictly, even the emission half of a luminescence instrument is a kind of spectrophotometer.
Spectrophotometry
Dosimetry
Enzyme assay
Latex fixation test
Biological small-angle X-ray scattering
Fluorescent treponemal antibody absorbtion 
Near infrared spectroscopy
Dark field microscopy