Black Light – 1926

“Invisible” Light Brings Interesting Speculation in Scientific World

By Herbert S. Marshutz,
A. BM D. Opt.

From American Cinematographer March 1926

THE old saying “there is nothing new under the sun” is sometimes contradicted. To state that white lamp black has been invented might inspire you to laugh or tap your forehead significantly. We can say, however, that “black light” has been discovered and you should not laugh because it is scientifically true.

Black light! Sounds just as ridiculous as white lamp black.
At first thought, one might conclude that black light must be the light in a totally dark room. Thinking about such a problem is a good deal like trying to determine whether there really is sound or not, when a book falls on the floor in a room where no one is within ear-shot.

Mixture of Colors

But black light has nothing to do with light in a dark room. All light – sun light and artificial light – being a mixture of all colors, the more thoroughly and correctly the
colors are mixed according to nature’s formulae, the whiter the light.

Rainbow Effect

Now if white light is broken up iinto its component colors by means of such a simple device as a prism, or a very complicated delicate instrument such as a spectroscope, the rainbow effect obtained is the spectrum. The rainbow is of course nothing more than the light of the sun broken up in to the various colors that make it white – the familiar red-yellow-green-blue-violet, each color with a different rate of vibration speed .

Light Invisible to Eye

These colors are all that the eye can see.
With instruments however, light that the eye cannot see can be measured and photographed. This light is both at the red end and at the violet extremity of the spectrum.
We have known of this invisible light and have called it infra-red and ultra-violet, respectively. But because it cannot be seen, has no quality of illumination or color, British scientists have appropriately called it “black light.”

Vibrations

The characteristics ,of black light are as well known as our old friends infra-red and ultra-violet. The former has a lower vibration rate than its neighbor, red, and the latter vibrates at a higher rate than violet, but not as high as the X-ray. Still faster than even the X-ray are the gamma rays of radium, vibration at some 150 quintillion times a second.
According to calculations in ”The Forum”, the pendulum of a clock would have to swing for over a billion years to make as many back
and forth motions as the gamma ray does in a single second.

Scientific Attention

Invisible light, unknown and then considered of minor importance for decades, is now holding the center of the world’s scientific stage. Employment of ultra-violet and infrared rays for invisible long distance signalling has been reported. The highly exploited but still mysterious ”death rays” intended to destroy an aeroplane in midair, etc., depend upon ”black light.” Still more recent honors have come to invisible light, with the announcement of unusually successful celestial photographs employing infra-red rays. Perhaps the real story of life on the planets will be revealed when black light is sufficiently understood and controlled to provide detail photography over millions of miles.