How Does a Spectrometer Work?

How a Spectrometer Works
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What Is a Spectrometer?

A spectrometer is a measuring device that collects light waves. It uses these light waves to determine the material that emitted the energy, or to create a frequency spectrum. Astronomers make the most frequent use of spectrometers to determine the makeup of stars or other celestial bodies. When objects are hot enough, they emit visible light at a given point or points on the electromagnetic spectrum. Spectrometers split the incoming light wave into its component colors. Using this, they can determine what material created the light.

Layout of a Spectrometer

The most basic design of a modern spectrometer is an assembly of a slitted screen, a diffraction grating and a photodetector. The screen allows a beam of light into the interior of the spectrometer, where the light passes through the diffraction grating. The grating splits the light into a beam of its component colors, similar to a prism. According to the University of Arizona (reference 1), many spectrometers also have a collimating mirror that makes the light waves parallel and coherent, thus making it more focused. This applies especially to spectrometers used in telescopes. The light then reflects onto a detector that picks up individual wavelengths.

Uses for Spectrometers

According to NASA (reference 2), spectroscopes can determine atmospheric composition by analyzing the wavelengths of absorbed sunlight that passes through a given section of the atmosphere. When light passes through a gas, like oxygen or methane, the gas absorbs some of the wavelengths. This is viewed as different colors, depending on the gas.