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Lamps provide the light in the ultraviolet/visible light spectrophotometer.

Particular wavelengths of light can be selected using a monochromator.

A photodetector receives the light and converts it into electrical signals.

A computer analyses the signals from the photodetector and displays the spectrum on a screen or chart recorder.

The light emerging from the monochromator can be split into two paths using a beam splitter.

The two beams of light are directed through the spectrometer using a series of mirrors or lenses.

The substance under test is dissolved in a solvent and placed in a glass or quartz test-tube, called a cuvette.

A cuvette containing the solvent alone is used as a reference.

Light passes from the lamp through the monochromator. One path takes it through the solvent in the reference cell to the photodetector.

Electrical signals pass to the computer and recorder.

The other path takes the light beam through the dissolved substance in the sample cell to the photodetector.

The beam splitter enables the computer to compare the spectra of light emerging from the sample and the reference, so that the final spectrum corresponds to the sample substance alone.

The beam splitter enables the computer to compare the spectra of light emerging from the sample and the reference, so that the final spectrum corresponds to the sample substance alone.

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