cuvette
/ kyoo-VET /
A cuvette is the little clear cup that holds your liquid sample in the path of the light beam — think of it as a precision-made shot glass whose only job is to sit still and stay transparent while light passes through.
It is a small container, usually square in cross-section, made of optically clear material and built to a fixed internal width — most commonly 1 centimetre — so that the path length in Beer-Lambert law is known exactly. Its two polished, parallel faces let the beam enter and leave with as little distortion as possible.
The cuvette quietly controls measurement quality. Fingerprints, scratches, bubbles, or a cell turned the wrong way all scatter light and corrupt the reading, so analysts handle cuvettes by the frosted sides, wipe the clear faces clean, and always insert them the same way round.
For UV work the analyst reaches for a quartz cuvette rather than a glass one, because glass absorbs ultraviolet light and would block the very wavelengths being measured.
Quartz for UV, glass or plastic for visible — match the cell to the wavelength.
Sample and blank should be measured in matched cuvettes — ideally the same one, rinsed — so that the cell itself contributes the same tiny absorbance to both and cancels out.