Newton's Theory The Pure Coloured Light Beam example essay topic

Introduction When I was a little kid I used to have a kaleidoscope (a cylinder with mirrors in it, at one side there where all kinds of coloured beads and at the other side you could look through it. When you looked through it and turned it round, you saw all kinds of coloured figures.) After I looked through it for the first time I desperately tried to find out how it worked and where all those beautiful coloured figures came from. I understood that it had something to do with light and darkness, because there appeared no coloured image when I put my hand before the side where the light was going into the cylinder. It had also something to do with the beads, because one of my friends had a kaleidoscope without beads (he was always very rude with his toys so think he smashed his kaleidoscope against the wall or something) and it appeared that it didn't work anymore. It was during physics class at secondary school that I learned more about colours. We did an experiment with a prism just as Newton did.

We had a ray of white light that went through a prism and was projected on a white screen. On the screen we saw the colours of a rainbow. With the use of a lens and a second prism we were able to recompose this "rainbow" into white light. My physics teacher told me that the prism decomposed the white light into its spectral colours because all the colours have a different wavelength and thus have a different refrangibility. But still coloured light remains a weird thing to me Goethe's theory of colours Most people know Johan Wolfgang von Goethe as a famous German writer, but to Goethe himself, his Theory of Colors was the work that he believed had earned him a major place in world history. "Of whatever I have achieved as a poet I have no high opinion at all", Goethe said in his Conversations with Ecker mann.

"There were excellent poets living alongside me, there were even more excellent ones before me, and there will be such poets after me. But that in my century I alone am the one who in the difficult science of color theory knows the truth -- that I consider a feather in my cap, and I therefore have a sense of superiority over many". Figure 1: Johan Wolfgang van Goethe Experimenting with a prism The colours of renaissance paintings and the Italian landscape fascinated Goethe. Because of this he wanted to know more about colours and he recalled his study of physics at the university of Leipzig, yet he could not remember the experiment that proved Newton's theory about colours.

Therefore he decided to do such experiments for himself. He borrowed a prism from a friend (C.W. B"uttner) and he prepared a room as a camera obscura, covering the one window with a sheet of metal with a small hole in it so that the sunlight could only enter the room through the hole. Figure 2: a schematic view of a white light beam going through a prism However before he could pursue the experiments, he moved. Then too B"uttner wanted his prism back so he sent a messenger to get his prism back.

When Goethe was walking to the door with the box in his hands he couldn't resist the temptation to look through the prism. He picked it from the box looked through it and expected to see everything coloured. But the white wall remained as white as it was and the same beholds for the dark areas. He walked to the window and also the grey sky remained un coloured. Only where dark and light surfaces met each other he saw colours. "But how surprised I was to see that the white wall which I looked at through the prism stayed white as before, that only where a dark part touched would a more or less distinctive colour be visible, and that the windowsill seemed quite brightly coloured while not a trace of colour could be distinguished in the grey sky outside.

There was no need for lengthy deliberation; I acknowledged that the production of colours requires a boundary, a frame, and instinctively cried out that the Newtonian doctrine must be false". Goethe thought that what he saw was in conflict with the theory of Newton. He thought that what Newton saw was caused by the little hole. The prism didn't change the natural light, as he saw for himself. What he saw was according to him the primary phenomenon. He convinced the messenger to not take the prism and he started his experiments.

Tensions According to his experiment Goethe thought that colours arose from the polarity between dark and light. He thought that there was some kind of tension between them and this is why you could only see colours at the border between dark and light surfaces when looking through a prism. According to Goethe it was a mistake to dismantle natural phenomena because he believed that there was a great grand phenomenon that you can only observe in its totality. When you would dismantle it further it wouldn't lead you to a deeper truth.

In Newton's theory the pure coloured light beam of one single wavelength would be the simplest phenomenon, but in Goethe's theory this was the white daylight. Goethe published his Beitr " age zur Optik with a set of twenty-seven cards to be viewed through a prism (figure 3) so that readers might repeat the experiments and confirm for themselves the validity of his account. Figure 3: on the right side you see how the images from the left side would look like when viewed through a prism. Goethe's theory and colour perception It is still thought that Goethe's theory, from physical perspective, doesn't make any sense at all (although many people are still inspired by it). Still there are some phenomena that can be better explained with Goethe's than with Newton's theory. Goethe expanded his theory so that he could also explain some visual phenomena with it.

He provided an efficient experiment for producing coloured shadows: two candles (A and B) on each side of a white tabletop, a pane of coloured glass placed before one (A) will have the "geforderte Farbe" and the shadow cast by candle (B) will have the "fordernde Farbe". With a red glass, for example, the candle will cast a green shadow. This experiment has been cited in recent years to explain Edwin Land's demonstration of a coloured photographic image cast by projecting two black and white slides and placing a colour filter on one of the projectors. You see a coloured image, but it is not really there Mondrian-like collages were key elements of Edwin Land's experiments on color vision.

The Mondrian's were illuminated by the three projectors at the bottom with light comprising various proportions of short, medium, and long wavelengths (figure 4). A telephoto meter, seen on a tripod to the right, measured the wavelength composition of the light reflected from a given colored patch to the eye. Land thereby showed that the perceived color of the patch is not determined by the wavelength composition of the light reflected from it. (Photograph by J. Scarpetti, courtesy of the Rowland Institute, Cambridge, Mass.) The "retin ex" theory of color vision that Land developed on the basis of his experiments has two essential elements: It recognizes lightness (that is, reflectance) as the fundamental stimulus of color, and it emphasizes the importance of boundaries, which allow the eye to estimate lightness by seeking out singularities in the ratio of energy flux from closely spaced points. The parallel with Goethe's theory, which itself emphasizes the crucial roles of lightness and of boundaries, is striking. Figure 4: Edwin Land's experiment Conclusion (contrasting research strategies) Newton's and Goethe's respective approaches to colour illustrate two very different approaches to experimental research.

Newton's approach is theory-oriented and Goethe's exploratory oriented. Theory-oriented experimentation is often regarded as the only relevant kind: It corresponds roughly to the "standard" view in the philosophy of science that experiments are designed with previously formulated theories in mind and serve primarily to test or demonstrate them. With exploratory research the focus is less on the connection between isolated experiments and an overarching theory, and more on the links among related experiments. What I personally think is that a theory could also just explain what you see without dismantling the whole phenomenon. When I had to explain, for example, to my little sister why she sees these beautiful coloured figures when she looks through a kaleidoscope, I wouldn't say that this is because all the beads reflect different kinds of wavelengths of the white light that falls in it through the hole and so on... No I would just say to here that it is because of the beads and the light.

Sources o Inspiratie uit het onbekende, (1967), J. Hilgevoord, N.V. Noord-Hollands che uitgeversmaatschappij, Amsterdam o Berwick, F. (1986) The Damnation of Newton: Goethe's Color Theory and Romantic Perception. Berlin / New York: De Gruyter, p. 9-25 o web.