Copyright © LightForm Inc, 2011 LightForm Inc: PARISS® Analytical Spectral and Hyperspectral Imaging 1st Order (nm)    200     400     600      800     1000    10 2nd Order      (100)    200     300     400       500      5 3rd Order      (66.6)   (33.3)  200     266.6   333.3             3.3 4th Order      (50)      (100)   (150)   200      250      2.5 ND = Nominal dispersion in nm/mm () Wavelengths absorbed in air All the above wavelengths are in nm N.D (nm/mm) Entrance slit Exit slits or detector elements Diffraction Grating Diffraction Grating Orders Explained Grating and Prism Characteristics Grating normal These and other grating characteristics are covered in the resources page Mini-tutorial