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On This Day: Scientist Wilhelm Roentgen Discovers X-Rays

Written By Caleb March
Last updated: February 13, 2023

On Nov. 8, 1895, German scientist Wilhelm Roentgen’s experiments with cathode rays led him to discover X-rays, a feat that earned him the first-ever Nobel Prize for Physics.

Discovery of the X-Ray

In 1895, Wilhelm Conrad Roentgen was the director of the physics department at the University of Wurtzburg and an active professor there. He had for some time been experimenting with a Lenard tube to produce cathode rays.

On Nov. 8, Roentgen was doing experiments in his darkened laboratory that involved covering the Lenard tube with lightproof paper and projecting the cathode rays onto various objects. Roentgen was surprised to see a piece of fluorescent material glowing under exposure to the cathode rays. He repeated the experiment, moving the fluorescent material further and further away from the Lenard tube. He noticed that the fluorescent material glowed up to two meters away from the Lenard tube’s cathode rays.

Roentgen knew that the cathode rays could not penetrate the lightproof covering over the Lenard tube, so he hypothesized that the glowing of the fluorescent material must be the result of some new kind of radiation. He began experimenting with putting different materials and objects between the Lenard tube and the fluorescent material and observing how the radiation passed through them.

It wasn’t until he had his wife put her hand in the path of the cathode ray that Roentgen made his famous discovery. The shadows from his wife’s hand over a photographic plate clearly showed the bones inside her hand and her wedding ring, while her flesh became transparent.

Roentgen named his discovery X-rays because of their unknown properties. On Dec. 28, 1895, Roentgen published his first paper on X-rays and subsequently received dozens of scientific prizes and awards. Most notably, Roentgen was awarded the first-ever Nobel Prize in Physics in 1901 for his work.

Early Use of the X-Ray

Sources in this Story

  • Lixi: X-Ray History
  • Nobel Foundation: Wilhelm Conrad Röntgen
  • Stanford University: Beam Line: Early History of X Rays (PDF)
  • Integrated Publishing: Radiological Safety Training for Radiation-Producing (X-Ray) Devices
  • U.S. Food and Drug Administration: Radiological Health Program: Medical X-Rays

One of the first radiology departments was set up at the Glasgow Royal Infirmary in 1896, where many experiments used X-rays to show various injuries and abnormalities. World War I played an important role in expanding the use of X-ray machines, which were used to find and remove bullets and shrapnel.

Allied forces began collaborating on the production of X-ray machines and trained radiologists were one of the most sought-after specialists on the front lines, second only to surgeons. After the war ended, the returning veterans brought stories of the X-ray machine back to America and helped spread knowledge of the invention’s usefulness and practicality.

Harmful Effects of X-Ray Exposure

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As early as 1896, technicians working closely with X-rays began reporting skin damage, and scientist Thomas Edison made reports of eye irritation from working with X-rays. Other reports quickly began to circulate about hair loss, lesions and cancer caused by excessive exposure to X-rays.

More efficient equipment and precautionary measures have significantly reduced the potential harm of X-ray machines. According to the Food and Drug Administration, the health risk posed by X-ray machines is fairly small.

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