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Durand, Loyal, Jr. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XXXI (1938)

James, Harry Raymond; Birge, Edward A.
A laboratory study of the absorption of light by lake waters,   pp. [1]-154 PDF (46.6 MB)


Page 11

 11~A LABORATORY STUDY OF THE ABSORPTION OF LIGHT 
BY LAKE WATERS 
PART I. PERCENTILE ABSORPTION OF RADIATION IN THE 
VISIBLE SPECTRUM 
HARRY R. JAMES 
INTRODUCTION 
 The transmission of white light through a material medium is always accompanied
by the loss of some of the radiant energy by absorption; that is, some of
the energy is transformed into heat, chemical energy, or to some other frequency
of radiation. When the light passes through a medium which transmits all
wave-lengths uniformly the emergent light will still be white; but if some
part, or parts, of the spectrum are absorbed more than others the phenomenon
of selective absorption is observed by the absence, in the transmitted light,
of the wave-lengths so absorbed and the medium will show a color that is
determined by the wave-lengths transmitted. All transparent media exert a
selective action in some part of the spectrum, though the action may not
be in the visible region. 
 Pure water exerts a selective action which varies greatly throughout the
visible spectrum. It is very transparent to blue and violet but absorbs red
very strongly. If a material which affects the transmissiOn of light in any
way is mixed with the water, the effects of the water and of the material
will be added and a new absorption spectrum will be given. 
 The present study was undertaken at the suggestion of Dr. E. A. Birge, biologist
of the Wisconsin Geological and Natural History Survey, with the purpose
of investigating the selective action on light of waters from the inland
lakes of Wisconsin, with particular reference to the effect of coloring matters
contained in the waters. The work is part of the study of the transmission
of radiation in the waters of inland lakes, which has for many years been
conducted by Dr. Birge and Dr. C. Juday. They have been attempting to determine
the quantity and the composition of the light found at various depths in
these lakes; with 


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