UV-visible spectrometers can be used to measure the
absorbance of ultra violet or visible light by a sample,
either at a single wavelength or perform a scan over a
range in the spectrum. The UV region ranges from 190
to 400 nm and the visible region from 400 to 800 nm.
The technique can be used both quantitatively and
qualitatively. A schematic diagram of a UV-visible
spectrometer is shown above.
The light source (a combination of tungsten/halogen
and deuterium lamps) provides the visible and near
ultraviolet radiation covering the 200 – 800 nm.
The output from the light source is focused onto the
diffraction grating which splits the incoming light into
its component colours of different wavelengths,
like a prism (shown below) but more efficiently.