Visible and Ultra Violet Spectroscopy:

Visible and ultra violet spectroscopy is one of the oldest types of spectroscopy, but its use in recognizing the structure of organic compounds has waned with the advent of more current spectroscopic techniques. However, vis-uv spectroscopy can still be a worthwhile tool for the organic chemist, particularly in the structural analysis of organic molecules that consist of extended conjugated systems. This generally takes place when functional groups like alkenes, ketones, aldehydes, carboxylic acids, esters and aromatic rings are in conjugation with other unsaturated systems.  

While electromagnetic radiation in the visible-uv region is absorbed through a molecule, the energy that is absorbed excites electrons from low electronic levels to higher ones. For this reason, visible and UV spectra are frequently called electronic spectra.