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Updated: June 13, 2025
He also discovered that these rays were capable of exciting fluorescence in some substances, that is, of causing them to emit light and become luminous, and that these rays, like the rays of light, were capable of affecting a photographic plate. From these properties two curious possibilities arose; namely, to see through opaque bodies, and to photograph the invisible.
All the visible light is cut out, leaving only the ultraviolet rays, and these travel as fast and as far, and return by reflection, as though accompanied by the visible rays." "But how can you see it?" asked an officer. "How is the ship it is directed at made visible?" "By fluorescence," answered Metcalf. "The observer is the periscope itself.
Phosphorescence and fluorescence seem especially to result from the alpha and beta rays, particularly from the alpha rays, to which belongs the most important part of the total energy of the radiation. Sir W. Crookes has invented a curious little apparatus, the spinthariscope, which enables us to examine the phosphorescence of the blende excited by these rays.
They gave him some pink fluid with a greenish fluorescence and a meaty taste, and the assurance of returning strength grew. "That that makes me feel better," he said hoarsely, and there were murmurs of respectful approval. He knew now quite clearly. He made to speak again, and again he could not. He pressed his throat and tried a third time. "How long?" he asked in a level voice.
His experimentation led him directly to the discovery of the important fact that no photographic apparatus of any kind is needed to enable an observer to use the X-rays in the delineation or inspection of objects through opaque substances. He said within himself: "Why not pass the X-rays through the object to be inspected and then convert them into visibility, as if by fluorescence."
President Morton has prepared for me a most beautiful example of such a design which, when placed in the violet light, exhibits a peculiarly brilliant fluorescence. From the experiments of Drs. Bence Jones and Dupré, it would seem that there is some substance in the human body resembling the sulphate of quinine, which causes all the tissues of the body to be more or less fluorescent.
Finally, in a tube exhausted as highly as possible, he obtained a faint fluorescent glow, like that produced in a Crookes tube. This fluorescence of the glass, according to Dr. Robb, invariably accompanies the discharge of Röntgen rays, and it is likely that these rays are produced more abundantly as the fluorescence increases.
It has been found that the immediate source of the rays is the fluorescence and phosphorescence of the glass, and they are more effective when the fluorescence is greenish-yellow or canary colour.
This scientific question Edison almost immediately solved. Fluorescence is a property which some transparent bodies have of producing, either on their surface or within their substance, light different in color from that of its origin. This happens, for example, when green crystals of fluor spar afford blue reflections of light.
A vacuum bulb connected between the discharge terminals of the high frequency coil, as shown in figure 101, was illuminated with a pink glow, which streamed from the negative to the positive pole that is to say, the cathode to the anode, and the glass became luminous with bluish phosphorescence and greenish fluorescence.
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