What is spectroscopy?
Spectroscopy is the technique of measuring the interaction of light with matter using an instrument called a spectrophotometer.
The two primary concerns are the wavelength of light incident on the sample and the type of physical interaction with the sample.
These physical interactions can be as varied as absorption, diffuse reflection, specular reflection, refraction, and scattering.
Spectroscopy can measure all common phases of matter (solid, liquid, gas). In many cases additional specialized accessories are required in addition to the spectrophotometer to measure the range of light interactions with the sample.