Man's physical universe

xanabras

408 ENERGY MAY BE PROPAGATED BY VIBRATIONS

telltale glow that will reveal the outcroppings of scheelite, a tungsten

ore.

Traces of oil in the mud obtained in oil wells may be detected by

the typical fluorescence in

ultraviolet rays.

Ultraviolet rays are used in making a rapid microscopic test of

sputum for the presence of tuberculosis bacteria. The sputum is

treated with carbol-auramin, which dyes the bacteria and causes them

to glow as bright yellow rods in ultraviolet rays. The use of this

technique has greatly decreased the time required for a sputum test.

Fig. 180. A portable ultraviolet kit for prospectors. (Courtesy of

Ultraviolet Products, Inc.)

The lens of the eye is markedly fluorescent, and a light haze in the

lens is observed in ultraviolet rays. A special ultraviolet lamp is used

to cause the eye to fluoresce and thus helps in cataract surgery.

Novel outdoor advertising signs have been made possible by the use

of fluorescent paints and lacquers and ultraviolet lamps. The whole

sign will appear the same at night as in the daytime when in the light

from ordinary incandescent light bulbs; but when these lights are

turned off, only those portions of the sign painted with fluorescent

paints will glow in the radiations from ultraviolet lamps. During the

day the fluorescent materials are invisible.

Designers of zeon advertising signs paint miniatures of these signs

with fluorescent paints that will glow in ultraviolet rays in such a way

as to show exactly how the zeon signs will look at night as well as in the

daytime.

The availability of powerful and economical sources of ultraviolet

radiations would make possible many other interesting light effects;

for example, whole ceilings could be constructed of glass panels coated

with fluorescent pigments and be caused to glow by ultraviolet sources

placed behind them, thus providing a source of diffuse light closely

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