Light and Colour In The Open Air

Minnaert's book is a classic; here are sketches of the book and its author

M. Minnaert (London: Bell and Sons, 1940, Reissued by Dover, 1954 and by Bell, 1959)
English translation by Kremer-Priest of De Natuurkunde van het Vrije Veld (Zutphen: 1937)
Dewey Classification: 535

Marcel Gilles Jozef Minnaert (1893-1970) b. Brugge, Belgium, educated at Univ. of Ghent (thesis on photometry in biology), where he supported replacement of French by Dutch during German occupation in the First World War as well as Flemish autonomy. Driven by the revanche to Holland, a country which has always been a defender of intellectual freedom, he settled at the University of Utrecht, where he took a degree and worked on solar physics, becoming director of the observatory in 1937. He was imprisoned by the Germans 1942-44 because of left-wing sympathies though never an activist. He spoke 10 languages, and enjoyed art and music. His wife was also a physicist, and he had children. [Encyclopedia of Scientific Biography]

The book begins with a short chapter on some easily made and understood observations that show how much can be learned by such methods, and reveals a world probably previously unknown to the reader. Then follow two chapters on the basic processes of reflection and refraction of light. This is applied to refraction in the atmosphere, which includes mirages and the green ray. Next is shown how to measure brightnesses, or at least to compare different sources, applying logarithms (to stellar magnitudes) and cross sections (opacity of woods). The eye and vision are next taken up, including acuity, Fechner's Law and the veil effect. The next chapter is devoted to colour, with sources, mixtures and the Purkinje effect. This facilitates a study in the next chapter of flicker, after-images and contrast effects important in many observations. Estimates of distance, shape and motion are then taken up. Now the reader is prepared for a long chapter on meteorological optics proper: rainbow, halo, corona. This is followed by another long chapter, where all the light phenomena of the sky are discussed: the blue sky, variations in brightness, colour and polarization, visibility, twilight and the zodiacal light. Phenomena of the landscape then follow, where colour is a predominant feature in everything that can be observed, including water in all its forms, and vegetation. The final chapter deals with light-emitting organisms and even the sparks made by striking rocks together. In the course of the book he shows how to make approximate measurements with simple devices, how to check many facts experimentally, how to use simple mathematics for better understanding, and above all, how to look and question. This is a remarkable book that can give a great deal of pleasure.

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Composed by J. B. Calvert
Created 28 March 2000
Last Revised 28 March 2000