Light is often broken down into specific regions of an "electromagnetic spectrum" by its wavelength. The spectrum below shows these regions with the highest energy (shortest wavelength, highest frequency) at the left. Notice that only a small portion of the spectrum (roughly 400 - 700 nm) represents visible light (Vis), the light our eye can detect.
Each region of the spectrum has a particular type of spectroscopy associated with it. We are interested in the UV and visible region. Light in this region of the spectrum causes changes in the electronic character of matter. In other words, it causes changes in the energy associated with the electrons in an atom or molecule.
