spectrophotometer
/ spek-troh-foh-TOM-eh-tur /
Think of a tiny optical assembly line: a lamp makes light, a colour-picker keeps just one shade, the sample steals some of it, and a light meter at the end reports what is left. A spectrophotometer is exactly that assembly line packed into one bench-top box.
Formally, a spectrophotometer is the instrument that performs spectrophotometry. Its core parts are a light source, a monochromator to select a wavelength, a holder for the cuvette containing the sample, and a detector that converts the surviving light into an electrical signal the instrument reads as transmittance or absorbance.
It is the everyday tool that turns Beer-Lambert law into routine measurements. Its accuracy depends on each part doing its job — a stable lamp, a clean wavelength, a properly placed cell — so warming the lamp up, zeroing on a blank, and keeping cuvettes spotless are the habits that separate good readings from bad.
Before reading samples, the analyst inserts a cuvette of pure solvent, presses 'zero', and lets the spectrophotometer set that as 100% transmittance — so every later reading reflects only the analyte.
Zeroing on a blank lets the instrument subtract everything but the analyte.
A 'spectrophotometer' measures light intensity for quantitation; a plain 'spectrometer' may only record where peaks fall. The names are often used loosely, so check what the instrument actually reports.