Spectrometers are used to measure light in terms of the electromagnetic spectrum. A spectrometer can measure a light’s intensity as well as its wavelength. These instruments are used in semiconductor spectroscopy and produce spectral lines as well as measure their wavelengths. They operate over a very wide range, from gamma rays to far infrared rays.

Different techniques are used to measure different parts of the electro-magnetic spectrum. Because of this, any specific spectrometry instrument will only be able to operate over a small portion of this vast range. When a frequency is below optical level, such as radio waves, a spectrum analyzer is preferred.

The average spectrometer uses an illumination from a light source through a slit which produces an object for the lens. This creates a parallel beam of light, producing a prism. The light then focuses on a specific point. Using the eyepiece lens, many images can be examined from the slit with various colors visible in the source.

Spectrometers spread light out into wavelengths, also known as spectra. Using these rainbow-colored bars, one can look for and study emission and absorption lines. These lines are the imprints of atoms and molecules that may be present. Each atom can only emit or absorb certain wavelengths of energy, thus the spectra is unique for each atom.

Photographic film has allowed for invention of the spectrograph. It was the first spectrometer to use a camera in lieu of a viewing tube. Now electronic circuits are used instead, allowing for greater accuracy and real-time spectrographic analysis. Photosensors are also used in place of film in spectrographic systems. Such spectral analysis, or spectroscopy, has become an important scientific tool for analyzing the composition of unknown material and for studying astronomical phenomena and testing astronomical theories. The wavelengths are measured with the spectrometer.