Grism (source code)
= Grism
{wiki}
A <grism> combines an <optical prism> with a <diffraction grating>. Their angular deviations can be chosen to cancel at a selected <wavelength>, while neighboring <wavelengths> emerge in different directions. This lets an instrument introduce spectral dispersion with approximately straight-through propagation at its design <wavelength>.
Inserting the <grism> into an imaging beam turns compact object images into dispersed <optical spectra>. The cancellation is wavelength-specific and order-specific: overlapping spectra and other <diffraction orders> remain potential sources of confusion. An <optical filter> can restrict the recorded band.
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