Newtonian optics. Photograph illustrating Newton's ideas on the origin of the spectrum. A large glass prism is seen resting on a page from Newton's book Opticks"of 1704, the whole lit by a spectrum. Isaac Newton (1642- 1727) was the first to show that white light was a compound of the spectrum of coloured light. This was against the view of Descartes that white light was modified by the medium through which it passed to form colour. Newton proved his theory by separating white light into a spectrum with a prism, then recombining the colours through a second prism to form white light."