Ultraviolet–visible spectroscopy or
ultraviolet-visible spectrophotometry refers to
absorption spectroscopy or reflectance spectroscopy in the
ultraviolet-
visible spectral region. This means it uses light in the visible and adjacent ranges. The absorption or reflectance in the visible range directly affects the perceived
color of the chemicals involved. In this region of the
electromagnetic spectrum,
molecules undergo
electronic transitions. This technique is complementary to
fluorescence spectroscopy, in that
fluorescence deals with transitions from the
excited state to the
ground state, while absorption measures transitions from the ground state to the excited state.