| Opticks; or, a treatise of the reflexions, refractions, inflexions and colours of light | |
| 1704 |  |
| Isaac Newton(1642-1727) | |
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From 1664 to 1665, young Newton read several books on optics, among them Descartes’s La dioprique, Keplar’s Optik and Hook’s Micrographia, that aroused his interest in the mathematical theory of reflection and refraction, as well as practical aspects of optics such as the grinding of lenses, innovation of the telescope, and observations of actual optical phenomena. It was in 1666 that Newton made one of the most important discoveries in the field of optics while striving to grind non-spherical lenses that would eliminate spherical and chromatic aberrations. He discovered that light could be dispersed by a prism into the colors of the spectrum, and then combined again with a white light through a second prism. He further verified that dispersed monochromatic color could not change color through the second prism and then disproved the long held theory that the colors of light were produced by the prism itself. With Newton’s demonstration that the colors of light were instead embodied in the white light, a revolutionary theory that denied the conventional theory of light modification was born. Newton first carried out this decisive experiment at Trinity College, Cambridge in 1666, then announced his theory before fellow members of the Royal Society five years later. The report immediately gave rise to keen controversies with other scientists. Newton was especially troubled with Hook’s confutation and the subsequent long argument with him that followed for several years. Newton also was irritated by Huygens’s indifference at that time. For this reason, he became reluctant to publish his scientific achievements for many years. It was not until over thirty years later that Newton published and fully discussed his achievements in optics in this book. In book I of this volume, Newton described the theory of geometric optics, and gave a detailed explanation of the above mentioned experimentation. Newton concluded here that it was impossible to make non-chromatic aberration lenses because each color had a different diffraction and he had failed to discover a type of glass with different dispersive power. He also proposed that light consisted of corpuscules which made it cast a distinct shadow when obstructed by other bodies. In book II, he dealt with the phenomenon of interference through the explication of his famous experiment the “Newton rings”. In this experiment he examined alternating patterns of bright and dark rings which were formed as a small curvature convex lenses was put on the glass plate through monochromatic light. If the rings were produced using white light, concentric colored rings appeared. This was caused by interference between the light reflected from the upper surface of the air film between the lenses and the glass plate and the light reflected from the lower surface of that. Newton geometrically calculated the thickness of air film with the known curvature of the lenses and the radius of rings. He discovered that the thickness of air for bright and dark rings can be defined as multiples of a variable a, in which the thickness of air for bright rings is equal to a multiplied by 1,3,5…, and the thickness of air for dark rings is equal to a multiplied by 2,4,6…, when a is the air thickness corresponding to the innermost ring. With this discovery Newton had demonstrated the periodicity of light. Newton investigated the problem of diffraction in book III, where he asserted his vibration theory of light for the explanation of the problem. In this theory Newton preserved the dominant corpuscule theory of light and synthesized that with the theory made by his contemporaries to explain the nature of light. These dual properties of light have now been fused into the modern theory of optics. The appendix of this book contains the first printing of two treatises on curve linear figures which contain Newton’s invention of ‘fluxional’ calculus. This, he stated, he had developed between 1665 and 1666, claiming priority over Leibnitz and raising a controversy which agitated mathematicians for nearly two centuries. This copy was presented by Newton to his friend Richard Bentley and is inscribed by the latter on the front end paper “Donum Auctoris Ri: Bentleio”. Richard Bentley (1662-1742), a scholar, critic and master at Trinity College, was responsible for recommending Roger Cotes to Newton as an editor for the second edition of the Principia. He also made Trinity College the earliest home of the Newtonian school by providing it with an observatory where Newton’s law of universal gravitation was confirmed through astronomical observations. |
