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The Biological Action of Light1

Naturevolume 115pages642645 (1925) | Download Citation



WHILE the heat spectrum, including infra-red, visible and ultra-violet rays, extends from a wave-length of some 60,000 to one of beyond the outer dark heat rays are the Hertzian waves used in radio with wave-lengths extending to a thousand metres or more. The inner dark heat rays merge into the visible, which are of wave-lengths from 700 pfi (red) to 400 /j,/j. (violet). Beyond the visible lie the invisible ultra-violet rays with wave-length from 400 /i/t to 100 /J./1, and beyond these come the soft X-rays and then the hard X-rays and the y rays of radium with wave-lengths so short as o-oi

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  1. F.R.S., National Institute for Medical Research



  1. Search for PROF. LEONARD HILL in:

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