Theory of Colours

Theory of Colours (Zur Farbenlehre in German) was a work published by Johann Wolfgang von Goethe in 1810. In the 1780's a number of statements as to the way colours arise came to Goethe's notice. Of the prismatic phenomena, it was commonly held that when you let colourless light go through a prism the colourless light is split up. For in such way the phenomena are interpreted.

Related Topics:
German - Johann Wolfgang von Goethe - 1810 - Light

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If we let a cylinder of colourless light impinge on the screen, it shows a colourless picture. Putting a prism in the way of the cylinder of light, we get the sequence of colours: red, orange, yellow, green, cyan, blue, violet.

Related Topics:
Colour - Red - Orange - Yellow - Green - Cyan - Blue - Violet

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Newton explained this by saying that the colourless light already contains the seven colours within itself - and when we make the light go through the prism, the prism really does no more than to fan out and separate what is already there in the light -- the seven colours, into which it is thus analyzed. A look through the prism, however, shows that we do not see white areas split into seven colours. Rather, we see colours at some edge or border-line.

Related Topics:
Newton - Colour

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If we let light pass through the space of the room, we get a white circle on a screen. Put a prism in the way, and the cylinder of light is diverted, (Figure I), but what appears is not the series of seven colours at all, only a reddish colour at the lower edge, passing over into yellow, and at the upper edge a blue passing over into greenish shades. In the middle it stays white.

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Goethe now said to himself: It is not that the light is split up or that anything is separated out of the light as such. In point of fact, I am projecting a picture, - simply an image of this circular aperture. The aperture has edges, and where the colours occur the reason is not that they are drawn out of the light, as though the light had been split up into them. It is because this picture which I am projecting - the picture as such - has edges. Here too the fact is that where light adjoins dark, colours appear at the edges. It is none other than that. For there is darkness outside this circular patch of light, while it is relatively light within it.

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The colours therefore, to begin with, make their appearance purely and simply as phenomena at the border between light and dark. This is the original, the primary phenomenon. We are no longer seeing the original phenomenon when by reducing the circle in size we get a continuous sequence of colours. The latter phenomenon only arises when we take so small a circle that the colours extend inward from the edges to the middle. They then overlap in the middle and form what we call a continuous spectrum, while with the larger circle the colours formed at the edges stay as they are. This is the primal phenomenon. Colours arise at the borders, where light and dark flow together.

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