![]() ![]() By moving the micrometer screw in one direction only to avoid the backlash problem, find a point where the dimmer bullseye lines are halfway between the brighter ones. One line of the doublet is twice as intense as the other, so that pattern is brighter. The doublet produces two bullseye patterns which overlap. Adjust the interferometer until you can see the bullseye interference pattern.ģ. This extended source can be used directly, so that no condensing lens or ground glass screen is needed. ![]() Place sodium lamp on side opposite micrometer screw. Align the mirrors with use of He-Ne laser.Ģ. Measurement of the sodium doublet with the Fabry-Perot interferometer is good preparation for the more difficult hydrogen/deuterium doublet measurement. HyperPhysics***** Physics 3901 ***** H/D Doublet Ground glass to aid focusing of line source (spectrum tube) Operating instructions for the M4 Spectrometer, Cenco Companyīulletin GB163-73A from Gaertner, which describes their Modular Interferometer (the one used in this experiment) Sodium light and helium-neon laser for test sourcesĬolored filters, red and blue (the red hydrogen interference filter is good for the red lines) HyperPhysics***** Class Home ***** Physics 3901Įquipment NeededFabry-Perot interferometer Carefully optimize the fringes for the H/D doublet and make several measurements of the wavelength separation. Measure the separation of the sodium doublet.ģ. Carefully align the mirrors with the aid of a helium-neon laser.Ģ. Measurement of the small H/D doublet requires high resolvance with the Fabry-Perot interferometer, so the following steps are recommended.ġ. The recommended experimental procedure below offers some helpful steps in the process. Since the measurement of the H/D doublet requires a well-aligned interferometer, it is good practice to align the spectrometer and measure the sodium doublet as preparation for the H/D measurement. Appropriate data can then yield the separation of the spectral wavelengths. The appearance of these rings depends upon the separation of the elements of the interferometer, i.e., the thickness of the air film between the surfaces. If another spectral line is present, a series of independent darker and lighter concentric rings can be seen. The expected interference fringe pattern from a single spectral line is a "bullseye" of concentric light and dark rings. Hydrogen/Deuterium Doublet Sodium and Hydrogen/Deuterium DoubletsĪ Fabry-Perot interferometer is used to separate the spectral lines of hydrogen from those of deuterium. ![]()
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