The Magic Rays of Ultraviolet

Science is changing the everyday life of people by putting ultraviolet rays, invisible to humans, to work in research, industry and medicine.

Stumbling over a mountainside in midnight blackness, a prospector suddenly shouted with excitement. In the darkness he had found a valuable mineral deposit that he had missed repeatedly in broad daylight.

In the completely dark cockpit of a military airplane, a pilot calmly examined a detailed map, without turning on a light.

A patient lies on the operating table. The surgeon pauses in the operation. Is the growth his scalpel has revealed cancerous? He must know the answer before he can determine the extent of the surgery needed. Experiments have shown that he may get it swiftly from a strange new microscope – one that uses light that man cannot see.

All this is not black magic, but something close to it. For by creating new kinds of lamps which use invisible rays, science has added a new dimension to human eyesight, with startling results in science, industry, medicine and people’s everyday lives. What science has discovered is remarkably easy to apply, for it is nothing more than a different kind of electric light.

The sharp-eyed genie in this modern Aladdin’s lamp was released when researchers in America’s big illumination laboratories were experimenting with metals and chemicals that might give off light when electrified.

Some were dismal failures, but they did something else that intrigued the engineers. Instead of the familiar kind of light that can be seen, they gave off rays called “black light”.

There is nothing mysterious about black light. Just as there are sound waves too high, and too low for the ears to hear, there are light-wave vibrations which the eyes are not equipped to see.


Some of these, the ultraviolet rays, are too short to be visible to the eyes, so they are called “black light”. When the rays are turned on ordinary objects, many of the objects change their appearance and reveal things about themselves that do not show up in ordinary light. Scientists must sometimes coat other objects with a fluorescent material, which gives off visible light when it is struck by a black light.

A shopper walking through a modern food store will see many foods that have been improved by the magic of invisible light. Any of the many products to which vitamins have been added, strangely enough, taste better because of the use of black light.

This started when one large company received complaints from customers, who agreed that the vitamin enriched product was undoubtedly more nutritious but said it sometimes had a strange taste.

Chemists told the food manufacturer what the trouble was some times the vitamin compound was not being thoroughly mixed in. If he could find the products in which it was improperly distributed he could stop the trouble. The researchers advised letting the products pass through a darkened booth, where they would be exposed to ultraviolet light. The ones containing the undistributed vitamins would glow.

A manufacturer who was offered a large shipment of olive oil wanted to be sure of its quality. It looked good, tasted right, but as a final check he had samples submitted to a food-testing laboratory. In a dark room, under black light the oil glowed blue and the testers shook their heads. “Cotton-seed oil,” they reported. Genuine olive oil, quite appropriately, has a greenish glow under the rays.

People generally may not know it, but the clothes they wear are protected by the uncanny talents of black light. Here is how it helped a clothing maker who had just purchased a large quantity of cloth. Fortunately for him, he was one of the many manufacturers who submit textile purchases regularly to the piercing scrutiny of ultraviolet rays.

Ultraviolet Uses

To the human eye and even to chemical tests, the cloth looked fine. But under black light, brightly colored spots showed up. The material was improperly dyed. The clothing maker refused to accept the shipment and customers were saved from buying garments that may not have withstood repeated cleanings.

Another textile-industry device that uses black light helps to protect people from falling in theaters and public buildings. A theater owner asked rug makers if they could not do something to take the danger out of darkness. What they provided is carpeting into which is woven fluorescent yarn. In the invisible ultraviolet rays from lamps in the theater ceiling, the yarns glow and softly light the floor.

As a new kind of detective, the trick of invisible chemical markings has put the finger on many unsuspecting criminals. One group of counterfeiters had worked out a scheme to fake the stock certificates of a company. Their multi-million-dollar scheme was instantly detected when a special code, visible only in black light, was found missing.

Police often use a powder which is invisible in ordinary light but which glows bright green in the rays of black light. It helped solve a series of thefts on the campus of a college.

As the thefts continued every student felt himself under suspicion, and the atmosphere was getting tense. Police placed a wallet containing money dusted with the invisible powder in a logical, tempting place. It soon disappeared.

Immediately, all students were asked to report to a specified building where each was examined under the searching rays of an ultraviolet lamp. The hands of two students glowed in the black light, and the case was solved.

Thousands of prospectors scrambling over mountains in the western part of the United States searching for tungsten now do their hunting at night. Scheelite, an ore from which tungsten is extracted, glows a brilliant blue when exposed to black light.

Surprisingly, one of the biggest deposits of tungsten, containing millions of pounds worth of the mineral, was “discovered” in Washington, DC, 2000 miles away from the deposit.

It happened when members of the US Geological Survey were prospectus in Idaho. They were not looking for tungsten but for antimony ore. As a matter of routine, they sent samples back to Washington for analysis.

There, scientists exposed the ore to ultraviolet light. To their surprise, it glowed a brilliant blue. It could mean only one thing – the prospectors had stumbled upon a tungsten find, as only scheelite glows with that particular color.

While working with black light, scientists discovered a surprising fact about human vision – some persons can actually see the black light which is invisible to most people.

University of Rochester (USA) scientists found that out during World War II, when they found what looked like a brilliant scheme for enabling aircraft to land on darkened carriers.

The idea was that an airplane would turn on a black light searchlight, the rays of which would strike fluorescent buttons arranged at intervals on the carrier.

Night Landing

A special system of mirrors would reflect the light back to the plane along a narrow beam invisible to an enemy plane, even if it were alongside a US Navy craft. Thus, to the pilot of a friendly plane, the earlier would appear to be outlined in visible light, while to the enemy plane it would be invisible.

Older scientists and admirals thought the system was wonderful, but some young lieutenants blasted the scientific plans. They announced they could see the ultraviolet searchlight on the approaching planes. Thus the naval experts learned that some people, particularly younger ones, and oddly often those with blonde hair, can see certain ultraviolet rays.

Their eyes lack a yellow substance which blocks out ultraviolet rays from most people’s vision.

Dr. Franz Urbach of the Kodak Research Laboratories in Rochester, in the State of New York, has had considerable success in finding other important jobs for ultraviolet. One of them puts the versatile vibrations to work in testing the stresses and strains of new machinery by a whole new science called “thermography”.

One may see how this works by visiting a darkened laboratory, loud with the clatter of a racing motor which is being tested. By coating the motor with phosphorus, and then turning black light on it, test engineers are able to get an exact picture of just what parts of the motor get hot, and how hot they get. Hot parts glow a dark blue; cooler ones, a light blue.

Nature herself has contrived to make black light play a fantastic role in everyday life. For this unseen radiation, which reaches the earth in sunlight, keeps people alive by creating the vital vitamin D.

Yet, strangely, this life-giver from the sun is also a potential killer. The sun sends out huge quantities of ultraviolet, most of which, though it comes smashing into the atmosphere, never reaches the earth. If it did, the strange effect that large amounts of ultraviolet have on living cells would kill them.

According to Dr. Rudolph Nagy, a black light specialist, when this highly energised, invisible light hits oxygen, it changes it into a different form, which is called ozone. And then, miraculously, the speeding rays are stopped by the tiny layer of this odd oxygen which they themselves have created.

The mystery of black light’s effect on living creatures is constantly being probed by science. In 1903, biologists discovered that when ultraviolet rays from the sun struck germs, the germs died. Something in these hurtling packets of energy could destroy life.

Working year after year in the laboratories of the Westinghouse and General Electric companies, researchers finally found out just which wavelengths of ultraviolet were the germ slayers. More patient work enabled them to create lamps that would give off these lethal rays.

The result is new safety in hospital operating-rooms, in the food industry, in the laboratories of pharmaceutical houses that make the Wonder drugs.

In the blue haze of death from ultraviolet lamps contaminating germs die before they can do harm. Now made in a simple, inexpensive form, the germ-killing lamps are adapted for home use. Already available in refrigerators, they promise to make the home of the future germ and virus free.

What will science do next with black light? Not even the experts can answer that question, but they are willing to predict that the magic light one cannot see is just getting started on its spectacular career.

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