GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY
Airy disk, Photo 2 of 2. A pinhole (small round aperture) is placed in a beam produced by either a Helium-Neon laser operating at 632.8 nm (red, Photo 1) or a Helium-Neon laser operating at 543.4 nm (green, Photo 2). The resulting Fraunhofer diffraction pattern, called Airy disk, is observed some distance away. The distance is the same for both lasers. The central diffraction lobe is slightly oversaturated so that the outer rings are more prominent. Note that the fringe spacing is smaller for the green laser.
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