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Discovery of X-rays

Posted in Historical articles, History, Medicine, Science on Friday, 29 April 2016

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This edited article about Wilhelm Rontgen and X-rays originally appeared in Look and Learn issue number 793 published on 26th March 1977.

 Wilhelm Rontgen, picture, image, illustration

Professor Wilhelm Rontgen and the all-seeing eye by Wilf Hardy

Professor Wilhelm Rontgen, a physicist at Wurzburg in Bavaria, leaned over the tube he was experimenting on and carefully covered it completely with black paper.

He had been working all day in his laboratory, and now it was late in the evening and getting dark. The tube he had covered so that no light could escape from it was called a Crookes tube, through which cathode rays are passed.

Rontgen, straightening up for a moment, saw before him in the gathering gloom, an extraordinary sight. Several yards away from him was a piece of cardboard he had been using in another experiment. The cardboard had been coated with a chemical which glows when light falls upon it. There was at that moment scarely any light at all in the laboratory, yet –

The cardboard was glowing!

Rontgen stared in disbelief. This was no ordinary light: it was bright green. But where was it coming from?

The only possible source of light in the laboratory was the Crookes tube, which he had just covered with black paper. Now Rontgen groped towards the tube and switched off the electricity supply to it. At once the green light from the cardboard went out.

When he switched it on again, the ghostly green light reappeared.

Puzzled, Rontgen held his hand between the tube and the cardboard screen. To his astonishment, the invisible rays of light which were apparently passing through the black paper, now passed right through his hand and cast a shadow of his bones upon the cardboard.

Rontgen had so little idea of what these rays were that he named them X-rays.

Rontgen reported his discovery to the scientific world, with the further news that the strange rays that passed through flesh would also make an impression on a photographic plate.

Armed with Rontgen’s information, scientists all over the world suddenly began to take never-before-seen pictures of the inside of the human body.

At once doctors put the new X-rays to use, detecting fractured bones. They were used so successfully that very soon deformed limbs resulting from fractures left undetected became very rare indeed.

X-Rays are caused by focusing fast-moving electrons, or cathode rays, at a metal target directly in front of them. They are produced when the electrons hit the target. An X-Ray lamp is simply a discharge tube arranged so that when the electrons hit a metal target, the X-rays caused by the impact bounce off sideways.

Rontgen’s amazing accidental discovery revolutionized the world of medicine. Six years after he made it he was awarded the Nobel prize for physics.

All his life Rontgen had been a scholarly man. A professor from the age of thirty, he announced his discovery of X-rays when he was fifty, and then wrote many important papers about his further experiments.

Soon after Rontgen’s discovery in 1895, it was realised that X-rays would detect a swallowed pin or metal object, and since then they have been used countless times for that very purpose.

Eventually doctors found that if a patient were given a meal of bismuth or barium compounds which are not transparent to X-rays, they could follow the course of food through the stomach and intestines and so trace the cause of digestive troubles.

It was also discovered that a heavy dose of X-rays has a usually destructive influence on the body. Some of the early experimenters, knowing nothing of these dangers, used the ray too freely and received burns and skin complaints.

Nowadays the tube of an X-ray machine is made harmless to its operators by being enclosed in a lead-lined box with a small ‘window’ through which the beams of rays pass out to the patient.

But extra powerful X-rays can be used to attack abnormal growth tissues of the body, and in this way many cures are effected without the aid of surgery.

X-rays are also used in industry. Modern methods have made it possible, for instance, for them to penetrate several inches of steel. In this way the rays can detect possible flaws in the castings of metal machine parts, which, undetected, could fly to pieces under pressure and cause great damage.

They are used to photograph the structure of precious stones, and for detecting faults in commercial products. They are even used by the art historian to examine the hardened pigment on old paintings. Does the picture he can see with his naked eye conceal a fine old master under its thick layer of paint? The wonderful all-seeing eyes of the X-rays will soon tell us the truth.

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