An alternative view of the history of optical diffraction emphasising a neglected observation first reported by Francisco Grimaldi.
Historical treatments of optical diffraction give due credit to Grimaldi`s work as predating, as early as the 1600s, the conventionally recognised authors, such as Huygens and Young. However, the scientific literature hardly acknowledged this and thereby overlooked the potential significance of the observation about the shiny spot at the edge of the half-plane in relevant diffraction experiments. The present work proposes that concentration on this spot may have an interesting role in an alternative approach to the subject. This paper reviews the correct order of the historical developments, revisits some prior experimental/theoretical works on the topic, and refutes the dismissal by Sommerfeld of the bright spot as an optical illusion. Impetus to the paper was given by a provocative question of a student regarding the postulate of virtual point sources in the simplified Huygens view of single slit diffraction patterns which one fails to observe.
Keywords: Observations and theories of Diffraction; Observations of Grimaldi, Young, and Huygens; Scalar Theory, Half Plane Sommerfeld’s solution, “reality” in Physics.
