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UV-Visible refers to absorption spectroscopy in the ultraviolet-visible spectral region.
This absorption directly affects the perceived color of the chemicals involved.
This technique is complementary to flourescence spectroscopy, in that flourescence deals with transitions from the excited state to the ground state, while absorption measures transitions from the ground state to the excited state.
Such shift is a change of spectral band position in the absorption, reflectance, transmittance, or emission spectrum of a molecule to a longer wavelength (lower frequency).
Because the red color in the visible spectrum has a higher wavelength than most other colors, this effect is also commonly called a red shift, although this usage is considered informal, and has no relation to Doppler shift or other wavelength-independent meanings of red shift.
This usage is often found in the scientific literature.
The tungsten filament lamp is commonly employed as a source of visible light.
This type of lamp is used in the wavelength range of 350 - 2500 nm.
The energy emitted by a tungsten filament lamp is proportional to the fourth power of the operating voltage.
This means that for the energy output to be stable, the voltage to the lamp must be very stable indeed. Electronic voltage regulators or constant-voltage transformers are used to ensure this stability.