Computer artwork of 19th century flint glass prism c. 1790, mounted on a rotating brass stand, of a type used to repeat experiments by Sir Isaac Newton. A narrow slit of light from the sun is focussed along the length of the prism from above, which is refracted by the prism into the colour spectrum and projected onto the surface below. In Isaac Newton's time, it was believed that white light was colourless, and that the prism itself produced the colour. Newton's experiments convinced him that all the colours already existed in the light in a heterogeneous fashion, and that \corpuscles\" (particles) of light were fanned out because particles with different colours travelled with different speeds through the prism. It was only later that Young and Fresnel combined Newton's particle theory with Huygen's wave theory to show that colour is the visible manifestation of light's wavelength.."