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diffraction grating

 Definition/Summary A diffraction grating is formed by an evenly spaced series of lines, slits, or other periodic array of reflective or transmissive elements. It is typically used for analyzing the spectrum or measuring the wavelength of electromagnetic waves, particularly in or near the visible part of the spectrum.

 Equations For a normally incident wave, waves are diffracted at angles such that $$d\ \sin \theta_m = m\ \lambda$$ where m is any integer. For other angles of incidence, the diffraction condition is $$d\ ( \sin \theta_m - \sin \theta_i ) = m\ \lambda$$ For nonzero m, a requirement for diffraction is $$d > \lambda$$

 Scientists David Rittenhouse (1732-1796) Joseph von Fraunhofer (1787-1826)

 Recent forum threads on diffraction grating

 Breakdown Physics > Classical Optics >> Diffraction

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 Extended explanation Definitions of termsθm = diffracted angle of mth-order wave θi = incident angle of wave m = (any integer) order of the diffracted wave λ = wavelength d = line spacing, or period of diffractive elementsNote: it is common practice to specify the number of lines per mm, cm, or m for a diffraction grating. This is simply the reciprocal of d; eg. a 1000 lines/mm grating has d=0.001mm Reflection and transmission A diffraction grating may work either in reflection or transmission, as shown here:

Commentary

 Redbelly98 @ 09:03 AM Oct11-10 Oct. 11, 2010: had to edit-and-save the "Equations" section in order to get LaTex to display properly. No changes made.

 Redbelly98 @ 03:45 PM Feb6-09 EDIT Images - added figure #1 A reflection grating and a transmission grating, showing d, θi, and θm.

 Redbelly98 @ 01:01 PM Jan24-09 When "diffraction grating" occurs in a post, the autolink is to the diffraction library entry. However, a 2nd occurrence of "diffraction grating" in a post does link to diffraction grating.

 Redbelly98 @ 03:37 PM Jan23-09 Entry created 23 Jan 2009 by Redbelly98