The Discovery of X-Rays

After reading this section you will be able to do the following:

  • Summarize how Roentgen discovered the X-ray.
  • Discuss the impact Roentgen's discovery had on the world at that time (1895), and then compare it to the impact it still has today.

First, the discovery of X-rays

An image of W.C. Roentgen In late 1895, a German physicist, W. C. Roentgen was working with a cathode ray tube in his laboratory. He was working with tubes similar to our fluorescent light bulbs. He evacuated the tube of all air, filled it with a special gas, and passed a high electric voltage through it. When he did this, the tube would produce a fluorescent glow. Roentgen shielded the tube with heavy black paper, and found that a green colored fluorescent light could be seen coming from a screen setting a few feet away from the tube. He realized that he had produced a previously unknown "invisible light," or ray, that was being emitted from the tube; a ray that was capable of passing through the heavy paper covering the tube. Through additional experiments, he also found that the new ray would pass through most substances casting shadows of solid objects on pieces of film. He named the new ray X-ray, because in mathematics "X" is used to indicated the unknown quantity.

In his discovery Roentgen found that the X-ray would pass through the tissue of humans leaving the bones and metals visible. One of Roentgen’s first experiments late in 1895 was a film of his wife Bertha's hand with a ring on her finger (shown below on right). The news of Roentgen’s discovery spread quickly throughout the world. Scientists everywhere could duplicate his experiment because the cathode tube was very well known during this period. In early 1896, X-rays were being utilized clinically in the United States for such things as bone fractures and gun shot wounds.

Take a look at these early x-rays.

 An X-ray image of a foot inside of a shoe. This is one of the first X-ray images.                 This is an X-ray image of a coin purse and it's contents. This is one of the earliest X-ray images.                 This is an X-ray image of a hand wearing a ring. This is one of the earliest X-ray images.


  1. X-rays were discovered by William Roentgen while experimenting with a cathode radiation .