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THOMAS YOUNG (1773-1829) AND THE PHYSICS OF LIGHT

The revival of the wave theory of light, begun by Thomas Young (1773-1829), is one of the most important features of the history of the 19th century. Young pointed out that the dividing of a beam of light into a refracted ray at the interface between two mediums was to be expected from the wave theory but had not been satisfactorily explained on the corpuscular theory. In 1801, he presented to the Royal Society a paper "On the Theory of Light and Colors", in which he proposed the principle of the interference of two wave trains as an explanation of Newton's rings and the colors of thin plates.

From Newton's measurements of the thickness of the air layers necessary to produce the several colors, Young was able to compute wavelengths. In subsequent papers, he described the interference fringes which he had observed by placing hairs on silk threads in front of a narrow slit illuminated from the rear; he announced the change of phase on reflection; he explained diffraction bands by the principle of interference; and he showed that the spacing of these bands gave values of the wavelength agreeing with those obtained from Newton's rings and that, therefore, both phenomena must be due to a common cause.

But the dogmatic spirit in regard to scientific matters was not yet dead. Young's paper aroused a storm of protest, even of derision and abuse. He was attacked not by the church, as was Galileo, but by some of his scientific, or, more probably, pseudoscientific contemporaries. His chief assailant was Henry Brougham, afterward Lord Chancellor of England, who "reviewed" Young's papers in the /Edinburgh Review/. The nature of Brougham's attack is indicated by the following quotation: "We wish to raise our feeble voice against innovations that can have no other effect than to check the progress of science and renew all those wild phantoms of the imagination which Bacon and Newton put to flight from her temple. We wish to recall philosophers to the strict and severe methods of investigation." Although Young replied at length in a privately published pamphlet, it was a long time before public opinion was willing to receive his theories with an open mind.

Adapted from: F.K. Richtmyer et al: Introduction to Modern Physics. 5th ed. McGraw-Hill 1955, p.33.

Editor's note: Thomas Young (1773-1829) was an infant prodigy who matured into an adult prodigy. At Cambridge, he was called "Phenomenon Young". He studied and practiced medicine, but failed at it because of the apparent absence of a "suave bedside manner". But while still a medical student, he was the first to discover the manner in which the lens of the eye changes shape (accommodation) in focusing on objects at differing distances. And it was Thomas Young who in 1801 explained astigmatism as resulting from irregularities in the curvature of the cornea. The early rejection of Young's wave theory of light by his British contemporaries was due more to chauvinism than to reason: the particle theory of light was essentially British; the wave theory of light was essentially French. At the age of 41, Young abandoned both medicine and physics and devoted himself to an analysis of the Rosetta Stone. In 1818, he produced a classic paper on Egypt that laid the groundwork for the later definitive analysis of the Rosetta Stone by Jean Francois Champollion (1790-1832).