THE NEWTON 2-KNIFE EXPERIMENT - INTRICACIES OF WEDGE DIFFRACTION

About a century before Young's celebrated two-slit experiment, Isaac N ewton quantitatively investigated the diffraction of light from a wedg e aperture, but failed to understand the implications of his findings. We have reexamined this unusual system theoretically within the frame work of the Fresnel-Kirchhoff scalar diffraction theory, and experimen tally using a laser light source with pinhole spatial filter and CCD c amera. Both the far-field shadow region and near-field directly illumi nated region reveal aesthetically striking images that are deducible f rom the mathematical analysis, but whose interpretation is subtle and best elucidated by an alternative and less widely known perspective of diffraction. (C) 1996 American Association of Physics Teachers.