spectrometer

In physics and astronomy, instrument used to study the composition of light emitted by a source. The range, or spectrum, of wavelengths emitted by a source depends upon its constituent elements, and may be used to determine its chemical composition.

The simpler forms of spectrometer analyse only visible light. A collimator receives the incoming rays and produces a parallel beam, which is then split into a spectrum by either a diffraction grating or a prism mounted on a turntable. As the turntable is rotated each of the constituent colours of the beam may be seen through a telescope, and the angle at which each has been deviated may be measured on a circular scale. From this information the wavelengths of the colours of light can be calculated. Spectrometers are used in astronomy to study the electromagnetic radiation emitted by stars and other celestial bodies. The spectral information gained may be used to determine their chemical composition, or to measure the red shift or blue shift of light caused by the movement of astronomical objects towards or away from the Earth.