Page of diagrams from Newton's 'Opticks' containing firgures 1 to 3, (1704). Sir Isaac Newton (1642-1727) found that by refracting light through a prism white light was dispersed into its constituent colours. If one colour was selected and refracted through a second prism, no further colours were introduced, showing that colours were a property of light and not the prism. Newton's discovery that it was imposible to focus an image distinctly using a single lens led him to build the world's first reflecting telescope.
© Science Museum / Science & Society Picture Library