Physics & Astronomy ETDs

Publication Date



The purpose of this experiment was to observe the light diffracted into the geometrical shadow of a sharp and a blunt metallic straight edge using a polarized, very intense, highly coherent light source. The light source used was a ruby laser, and a Nicol prism was used to linearly polarize the laser light. Two polarizations of the laser beam were used: One with the E vector of the incident beam oriented parallel to the edge of the straight edge, and the other with the E vector oriented perpendicular to the edge. One photomultiplier tube was used to monitor the pulsed laser beam, while a second photomultiplier tube observed the diffracted light at various angles into the geometrical shadow of the straight edge. The output voltages from the two photomultiplier tubes were displayed together on a dual-beam oscilloscope and photographed. The ratio of these two voltages was the ratio of the intensity of the incident laser beam to the intensity of the light diffracted at various angles into the geometrical shadow of the straight edge. Two significant problems were encountered in performing this experiment. The first problem was that of eliminating light scattered into the photomultiplier tubes from obstacles other than the straight edge. This problem was solved by placing the straight edge and photomultiplier tubes inside a four foot cubic box lined with black velvet. The second major problem was that dust on the razor blade and dust in the atmosphere scattered light into the photomultiplier tubes. Dust on the razor blade was eliminated by washing it in alcohol. The dust in the atmosphere could not be eliminated and was, consequently, the greatest source of error. Results are compared with the experiment done by Jean Savornin and the theory of Póincaré and Ramen.

Degree Name


Level of Degree


Department Name

Physics & Astronomy

First Committee Member (Chair)

Howard C. Bryant

Second Committee Member

Christopher Dean

Third Committee Member

Victor H. Regener



Document Type