spectrometer
/ spek-TROM-uh-ter /
Hold a glass prism up to sunlight and the white beam fans out into a rainbow. A spectrometer is the laboratory version of that prism, built to do the splitting carefully and to measure exactly how much light comes out at each colour. Instead of you eyeballing the rainbow, a detector records a precise curve of brightness against colour.
More precisely, a spectrometer is an instrument that separates light (or other radiation) into its component wavelengths and measures the intensity at each one, producing a spectrum. A typical one has a source, a way to spread the light apart (a prism or, more commonly, a diffraction grating), and a detector that reads the signal. The term covers many machines that share this core job, from a desktop UV-visible unit to a research-grade infrared system.
Why it matters: because every atom and molecule absorbs or emits its own particular set of wavelengths, the spectrum is like a fingerprint. By reading which colours are missing or present and how strongly, chemists identify substances and measure how much of each is there. A caveat: the spectrometer only delivers numbers; turning those numbers into a chemical answer is the job of spectroscopic analysis, and a poorly calibrated instrument gives confident but wrong fingerprints.
A water-quality lab shines white light through a sample of treated water in a UV-visible spectrometer. A grating spreads the transmitted light, and the detector finds a dip at a wavelength absorbed by nitrate. The depth of the dip tells the analyst the nitrate concentration to a few parts per million.
The spectrometer turns an invisible chemical fingerprint into a curve you can read.
Spectrometer, spectroscope, and spectrophotometer are easy to mix up. A spectroscope just lets you look at a spectrum; a spectrometer measures wavelengths and intensities numerically; a spectrophotometer is a spectrometer specialised for measuring how much light a sample absorbs. In everyday lab talk these lines are often blurred.