Radiation can only affect matter if absorbed by it. Within the broad range of 300-1000 nm, which we call "the visible", light quanta are energetic enough to produce excited electronic states in the atoms and molecules that absorb them. In these states the molecules may have quite different properties from those in their dormant condition, and reactions that would not otherwise occur become possible. About 80 % of the radiant energy emitted by our sun lies in this fertile band, and so long as the sun's surface temperature is maintained at about 6000° C this state of affairs will continue. This and the transparency of our atmosphere and waters have allowed the generation and evolution of life. Before life began the atmosphere probably also transmitted much of the solar short-wave radiation, but with the rise of vegetation a new product - oxygen - appeared and this, by a photochemical reaction in the upper atmosphere, led to the ozone layer that now protects us from the energetic "short-wave" quanta that once, perhaps, took part in the generation of life-molecules. Light is an ideal sensory stimulus. It travels in straight lines at great speed and, consequently, can be made to form an image from which an animal can make "true", continuous and immediate assessments of present and impending events.
Authors and Affiliations
Department of Chemistry, Case Western Reserve University, Cleveland, USA
E. W. Abrahamson
Kerckhoff-Institut der Max-Planck-Gesellschaft, Bad Nauheim, Germany
Ch. Baumann
Department of Ophathalmology, New York University Medical Center, New York, USA
C. D. B. Bridges
Department of Zoology, University of California, Los Angeles, USA
F. Crescitelli
Medical Research Council’s Vision Unit, School of Biological Studies, The University of Sussex, Falmer, Brighton, UK
H. J. A. Dartnall,
J. N. Lythgoe
Department of Zollogy, University of California, Berkeley, USA
R. M. Eakin
Department of Biophysics, University College London, London, UK
G. Falk,
P. Fatt
Department of Biology, Yale University, New Haven, USA
T. H. Goldsmith
Department of Biology, Nara Medical University, Kashihara, Nara, Japan
R. Hara,
T. Hara
Division of Pure Physics, National Research Council, Ottawa, Canada
S. M. Japar
Department of Anatomy, School of Medicine, University of Pennsylvania, Philadelphia, USA
P. A. Liebman
Department of Zoology, The University of Liverpool, Liverpool, UK
R. A. Morton
Laboratory of Experimental Psychology, The University of Sussex, Falmer, Brighton, UK
W. R. A. Muntz
Trinity College, Cambridge, UK
W. A. H. Rushton
Department of Zoology and Comparative Physiology, Queen Mary College, University of London, London E. 1, UK
T. I. Shaw
Department of Physical Chemistry, The University of Cambridge, Cambridge, UK
J. R. Wiesenfeld
Department of Biology, Faculty of Science, Osaka University, Toyonaka, Osaka, Japan
T. Yoshizawa
Bibliographic Information
Book Title: Photochemistry of Vision
Authors: E. W. Abrahamson, Ch. Baumann, C. D. B. Bridges, F. Crescitelli, H. J. A. Dartnall, R. M. Eakin, G. Falk, P. Fatt, T. H. Goldsmith, R. Hara, T. Hara, S. M. Japar, P. A. Liebman, J. N. Lythgoe, R. A. Morton, W. R. A. Muntz, W. A. H. Rushton, T. I. Shaw, J. R. Wiesenfeld, … T. Yoshizawa
