The newer knowledge in the field of physics has brought about a recognition of the fact that in addition to the visible electromagnetic waves, the invisible infra-red and the ultraviolet light waves also have indisputable chemical and biologic effects. To these are sometimes added the influence of what has fancifully been called Roentgen "light," as well as the "gamma light" from radioactive substances. Electromagnetic waves, as Bovie1 has expressed it, have no effect on objects which are incapable of vibrating in resonance with them. The wave passes through the object, and the object is said to be transparent to the particular wave length in question; for example, rock salt is transparent to heat, to visible waves and to ultraviolet waves; ruby glass, to red light waves; paraffin wax, to hertzian waves; white fluorite, the most transparent substance known, to heat, to visible waves and to ultraviolet waves; thin deposits
LIGHT RADIATIONS AND PROTOPLASM. JAMA. 1915;LXV(7):624. doi:10.1001/jama.1915.02580070058017
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