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Natural Science Forum / Physics / Optics / May 2005What is a diffraction order?
But I came across the term "diffraction order" in literature, and I don't know what it means. Does it refer to the areas of diffraction maxima (as in the sin(x)/x Fraunhoffer pattern)? As in the large central maxima would be zeroth order, the two on either side would be 1st order, then 2nd order, etc. Or does it refer to the higher order terms in the expansion of Kirchhoff's diffraction integral? What is a diffraction order? Thanks! Pete "Diffraction order" refers to diffraction gratings, and the angles of the beams that are either reflected from or transmitted through them. A diagram would illustrate the concept better than I could describe with text alone. It might help for you to Google "diffraction grating" and look for a figure that explains the concept. At any rate, here is my text description of diffraction orders. Again, a diagram is really required to understand it: The (reflected or transmitted) beams from a grating have the following property: the optical path difference for adjacent rulings on the grating must be an integer multiple of the wavelength. This integer gives the order for that particular beam. So: The zero-th order beam has an optical path difference of zero between rulings, The first order beam has an optical path difference equal to one wavelength, The second order beam has ... two wavelengths, etc. etc. Mark > "Diffraction order" refers to diffraction gratings, and the angles of > the beams that are either reflected from or transmitted through them. [quoted text clipped - 20 lines] > > Mark Hi Mark, I believe I know which diagram you're talking about -- the one used to describe (for example) wave interference for Young's double slit, where you show that d \sin(\theta) = n \lambda. If so, then I totally understand your explanation. Thank you! Pete Yep, that's the diagram. Applies to diffraction gratings as well as to the double slit. For the diffraction grating, d is the spacing between adjacent slits or rulings. Mark p.s. You're equation confused me for a moment, as I interpreted the backslash as a "divided by" symbol. Many (most?) people using these usenet groups are in a text-only mode of viewing. > Hi Mark, > [quoted text clipped - 5 lines] > > Pete |
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