The Curie Method Educational content


German physicist Wilhelm Conrad Röntgen discovered X-rays on November 8th, 1895. Although these rays are invisible to the human eye, they can leave an image on photographic paper, just as sunlight does, and pass through opaque objects.

One of the first radiographs (X-ray images), of Albert von Kölliker’s left hand,
made by W.C. Röntgen during a public demonstration on January 23, 1896
Source: Wikimedia Commons

Röntgen’s discovery immediately spread through the international scientific community, in particular because of its main application, radiography. For X-rays, skin and flesh are virtually transparent, while bones are almost completely opaque. Illuminating the body with X-rays, therefore, yields a fairly clear photograph of the skeleton. It has major medical applications.

German physicist Wilhelm Conrad Röntgen in 1901,
the year that he received the very first Nobel Prize in Physics for his discovery of X-rays.
Source: Curie Museum (ACJC collection).

The discovery of X-rays inspired many scientists to study “invisible rays”. One of them, French physicist Henri Becquerel, discovered uranium rays in March 1896. This discovery was the starting point for the research of Marie and Pierre Curie. That same year, French doctor and radiologist Antoine Béclère performed the first radioscopic tuberculosis screening. The following year, he offered classes in radiology and later in radiotherapy.

We now know that X-rays are electromagnetic waves, just like visible light, infrared and ultraviolet rays, microwaves, radio waves and gamma radioactivity. What characterizes each of these electromagnetic waves is their oscillation frequency, measured in Hertz (Hz). In other words, it is the number of peaks per second that the wave has (1 Hz = 1 peak/second). The different frequencies account for the radically distinct physical properties found among these radiations.