Man's physical universe

xanabras

LIGHT IS A FORM OF RADIANT ENERGY 393

Moonlight effects are simulated in the movie industry by taking

infrared pictures in the daytime.

Many stars which are so cool that they do not emit visible light have

been discovered by infrared photography.

Infrared photography is very useful in examining paintings and in

the study of documents and textiles.

Fig. 169. The Sierra Nevada range in the vicinity of Yosemite, photographed

from Mount Hamilton by infra-red light; distance to Half Dome, 120 miles.

(Courtesy of the Lick Observatory.)

Infrared lamps are now widely applied in speeding up the baking of

enamels and lacquers on automobiles, refrigerators, washing machines,

and furniture. By the use of infrared lamps, sheet rubber may be cured

in two minutes instead of the two hours formerly required. These

lamps may even be used to bake cookies. Soon infrared lamps may be

used to dry the family washing or to keep one warm in cold weather.

An infrared telescope was patented in 1940. It is based on the fact

that fluorescence is speeded up by heat. The telescope focuses infrared

rays on a fluorescent screen which is

continually flooded with ultra^

violet rays. Where the infrared rays fall upon the screen, the fluorescence

^ increases, and the picture appears.

A closed automobile warms up when placed in sunlight because of

Fluorescence is the emission of visible light by an object which is irradiated with electromagnetic

radiations of shorter wave length.

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