2009 Advanced Laboratories Conference Abstract Detail Page

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Abstract Title: Using Longitudinal Laser Modes to Make Accurate Speed of Light Measurements
Abstract: An adjustable-cavity helium-neon laser is an excellent setup for providing undergraduates practical experimental and research experience.   In this study, a laser was constructed from a helium-neon plasma tube and a movable output coupler (99% mirror), thereby allowing the cavity length to be varied.  The laser beam from the cavity was directed onto a fast photodetector, the output of which went to a spectrum analyzer.  The longitudinal mode beat frequencies were measured on a spectrum analyzer, along with their corresponding change in cavity lengths.  With this data, and the refractive index of air derived from temperature and atmospheric pressure, the speed of light was calculated to an accuracy of better than 0.03% as predicted from the propagation of error.  This experiment demonstrates by optimizing measurement precision, very accurate results can be obtained.
Abstract Type: Poster
Contributed Poster: Download the Contributed Poster
Session: Session IX - Effective Experiments Poster Session

Author/Organizer Information

Primary Contact: James D. White
Juniata College
1700 Moore St. BAC
Huntingdon, PA 16652
Phone: 8146413545
Co-Author(s)
and Co-Presenter(s)
Mark J. Pearson, Justin T. Schultz, Daniel Sidor, Michael Best, and
Daniel D'Orazio