The phenomenon of knife-edge light diffraction was first described in 1665 by Grimaldi, who introduced the term diffraction to define this special kind of light propagation (differing from rectilinear propagation, reflection, and refraction). The concept of diffraction was elaborated on in detail by Newton. It is well known that Newton clearly understood that diffraction is caused by the steplike disrupting homogeneity of the space of the propagation of light, but he could not reconcile this fact with the law of rectilinear light propagation, which is not generally inherent in the wave motion observed in nature (waves at waters’ surfaces, tides, etc.). This was the main discrepancy between Newton’s understanding and Huygens’ explanation of the nature of light. Despite Newton’s discovery of two important optical phenomena (i.e., Newton’s rings and dispersion of light), both of which are now explained by wave theory, Newton hesitated to accept the wave paradigm and was often inclined to use the corpuscular interpretation. It is of interest that some late remarks made by Newton during the singular optics epoch2 give reason to believe that he was on the verge of accepting the wave understanding of light phenomena, at least in terms of the edge diffraction wave (EDW), which is the main topic of consideration here. Nevertheless, this statement seems hyperbolic, as Newton widely discusses the edge effect (rather than on the edge wave) and only uses the term ‘light rays,’ which is attributed to geometrical optics. As such, Newton’s views from those days can only too cautiously be projected to the modern views on the nature of light.
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