Slides (4 X 4) OF INTERFERENCE

            "Newton's Rings and Diffraction Photographs" by Prof. Fred A. Mobly, Dept of Physics, WVU

                      Newton's Rings by reflection on monochromatic light from a half platinized lens surface of 42 cm radius on a platinized flat. The 1000th ring has been located and photographed with the arrangement. Incident light was parallel and at normal incidence to the flat.

                      Diffraction of light (monochromatic from a pin hole source), on passing through circular openings, in this case the holes in a drill gage. Note that an odd number of half period elements in a wave front gave bright centers in the geometrical images of holes, while an even number of half  elements in a wave front gave dark centers in the geometrical shadows of the holes, as indicated at 1e, 2e, etc. on the slide. (No lens was used to obtain this effect).

                      A contact print to show the openings in a razor blade mounted over a hole in a board, and trimmed with black card board at the outer edges, diffraction for which is shown on the next slide.

                      Diffraction of monochromatic light from a pinhole source as it passes through openings of a razor blade and its masking. Note the overlapping of straight edge diffractions at corners, and the dark centers at certain points in the shadow of the openings. (No lens.)

                      Diffraction at a straight edge, actually at the rounded edge of a piece of strap iron. The bands seen are not in the geometrical shadow of the strap iron. Source was monochromatic light through a slit 0.012 cm wide. (This slide is rotated 90 degrees from what it should be to correspond to the slides which follow.) (No lens used to get this effect.)

                      Diffraction into the geometrical shadow of a slit whose width was calculated to pass through it only one-half period element in a monochromatic cylindrical wave front. Note two or more secondary diffraction maxima at either side of the central image of the slit. (No lens was used to get this effect.)

                      Diffraction of monochromatic light through a slit whose width was calculated to let through two half period elements from a cylindrical wave front. Note that the center of the geometrical shadow of the slit is dark. Imagine the slit divided into four strips and that the light in the two outer strips has to travel oneİhalf wave length farther than light from the two central strips to get to the center of the geometrical shadow of the slit, and thus the light from the four strips being in opposite phases (on the average) produces darkness at the center. (No lens used to get this effect).

                      Diffraction from a double slit. This really amounts to a regular transmission diffraction grating having only two slits, illuminated by monochromatic light from a narrow slit at the source of light. (No lens used to get this effect.) Other dimensional data is to be found on these slides if desired.