Recall how Newton's Investigation of light followed one form of the scientific method. Match the statements about Newtons experiment with the steps in the scientific method.
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His investigations into optics commenced in 1666 at the end of an annus mirabilis when, at home in Woolsthorpe, Lincolnshire due to the bubonic plague which was raging in Cambridge, he investigated gravity, calculus and the laws of motion. He determined to ‘try therewith the celebrated Phaenomena of Colour’. It had been thought previously that colour was created by the mixing of light and darkness. Newton noted, however, that the blended print on the white page of a book appears grey, not coloured, when viewed from a distance. His experiments in bending light through prisms led, eventually, to the revolutionary discovery of the existence in white light of a mixture of distinct coloured rays, distinguishable when refracted in a prism. In his first experiment he projected the light via a round hole in his shutters.
‘In a very dark Chamber, at a round hole, about one third Part of an Inch broad, made in the Shut of a Window, I placed a Glass Prism’. See Opticks, Prop. II, Theor. II Exper. 3. Newton began by projecting the light onto a wall before fixing the posture of the prism and projecting the light onto a white sheet of paper.
This produced a stretched image of the sun, which was mainly white, but featured a blue upper edge and red lower edge. In his second experiment he projected the light through a narrow slit in the shutters, thereby achieving the now familiar multi-coloured band. A painting in the BOA Museum shows Newton allowing light, via a prism, to reveal the spectrum on a piece of white card resting on a chair.
On his return to Cambridge Newton was unusually open about his discovery, demonstrating the prism experiment before his peers and showing that the colours could be recombined to form white light. He gave a detailed explanation of his discoveries in public lectures between 1669 and 1671 (published in 1728 as Lectiones Opticae) and in a paper to the Royal Society in 1672. In 1675, he presented another paper which described further experiments on the colour of thin films and plates, and which put forward a corpuscular theory of light which was surprisingly similar to the modern theory of light quanta. Newton’s Opticks, first published in 1704, went through many editions and was the most influential work on experimental science for almost all of the century. Amongst other things, it explained how raindrops refract sunlight to form rainbows. This was the first chromatic explanation of a phenomenon that had fascinated scientific writers, including Aristotle, Alhazen, Vitello and Antonio de Dominis, since the account of Noah’s Ark was first written down. He named the seven colours of the spectrum red, orange, yellow, green, blue, indigo and violet. These names have stuck, although the choice of seven should be seen as conveniently sacred, rather than a precise description of the visible spectrum. Close reading between the lines has shown that the Opticks is riddled with number symbolism. Newton also described how each colour of the spectrum merges gradually into its neighbour to give ‘hues’, though it was not until 1801 that Thomas Young, who had revived Huygens’ Wave theory of light, showed that the eye has three ‘cones’ or nerve endings to distinguish these hues.