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Unformatted text preview: Experiment 10 Diffraction Introduction This weeks lab covers interference and diffraction. There are two sections to the lab. In Part 1, you will be studying Fresnel diffraction and in Part 2, you will look at Fraunhofer diffraction. Fresnel Diffraction This part has two sections. In the first section you will study Fresnel diffrac- tion by a single straight edge and in the second section you will study diffraction by a single slit. 1 Edge Diffraction Procedure To start, place a laser with a spatial filter at one end of the optical bench. The filter is to ensure that no off axis modes from the laser are in the beam. This is important whenever the laser beam needs to be spatially coherent. That means that we want the beam to appear as if it comes from a point source. The spatial filter will be adjusted by your instructor before lab. Be careful! A slight bump can put it out of alignment. Since the filter works by focusing the beam through a 1 micron pinhole, you can guess how much fun it is to realign. Place a razor blade in the center of the beam and position it exactly 40 cm from the spatial filter. Try not to cut yourself. Exactly 40 cm beyond the razor blade place a photodiode which is mounted on a scanning motor that scans perpendicular to the beam. The diode will record the intensity of light as a function of distance. Record your data on the computer. The shadow of the razor blade should fall in the middle of the diode travel....
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- Fall '08