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The spectrometer uses a prism or a grating to spread the light into a spectrum. This allows astronomers to detect many of the chemical elements by their characteristic spectral lines. These lines are named for the elements which cause them, such as the hydrogen alpha , beta, and gamma lines.
A blazed diffraction grating reflecting only the green portion of the spectrum from a room's fluorescent lighting. For a diffraction grating, the relationship between the grating spacing (i.e., the distance between adjacent grating grooves or slits), the angle of the wave (light) incidence to the grating, and the diffracted wave from the grating is known as the grating equation.
A special form of a blazed grating is the echelle grating. It is characterized by particularly large blaze angle (>45°). Therefore, the light hits the short legs of the triangular grating lines instead of the long legs. Echelle gratings are mostly manufactured with larger line spacing but are optimized for higher diffraction orders.
The multiple-prism dispersion theory is applied to design these beam expanders either in additive configuration, thus adding or subtracting their dispersion to the dispersion of the grating, or in compensating configuration (yielding zero dispersion at a design wavelength) thus allowing the diffraction grating to control the tuning characteristics of the laser cavity. [11]
An ultrasonic grating is a type of diffraction grating [1] produced by the interference of ultrasonic waves in a medium, which alters the physical properties of the medium (and hence the refractive index) in a grid-like pattern. The term acoustic grating is a more general term that includes operation at audible frequencies.
An echelle grating (from French échelle, meaning "ladder") is a type of diffraction grating characterised by a relatively low groove density, but a groove shape which is optimized for use at high incidence angles and therefore in high diffraction orders. Higher diffraction orders allow for increased dispersion (spacing) of spectral features at ...
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A grism (also called a grating prism) is a combination of a prism and grating arranged so that light at a chosen central wavelength passes straight through. The advantage of this arrangement is that one and the same camera can be used both for imaging (without the grism) and spectroscopy (with the grism) without having to be moved.