Newtonian prism arrangement

2 Prisms in an arrangement devised by Isaac Newton to demonstrate that light dispersed, or split, into the optical spectrum by one prism, retains these dispersed colours when passed through a second prism. The image shows white light entering the left prism and being dispersed into the full spectrum. The second prism is positioned so that it intercepts only the yellow and red parts of the spectrum. These rays pass through the second prism unchanged in colour. 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."