Becquerel Discovers Another New Kind of Radiation


It has been less than four months since Professor Roentgen discovered the new kind of radiation which we now know as x- ray or Roentgen radiation. In the last two months we have observed the news of this discovery spreading around the world and how scientists and physicians are now working together to produce x-ray images of the human body for diagnostic purposes. During the month of March more experiments have been performed in many laboratories to demonstrate the characteristics of this new kind of radiation and its ability to produce useful medical images.

However, in the great excitement created by the discovery and applications of x-radiation, we should not overlook another discovery which might also lead to important medical applications. This is a discovery which was stimulated by the discovery of x-radiation and aided by a period of cloudy weather in France.

In the gas-discharge tubes which are being used by Professor Roentgen and many others to produce x-radiation there is also a fluorescent effect produced in the glass walls of the tubes. It has been shown that the actual source of the x- radiation is the brightly fluorescing area of the tube.

Several scientists have noted the association between the fluorescence and the production of x-radiation. Poincare had questioned whether materials which produce a strong fluorescence might also produce x-rays. He and others have attempted to detect x-radiation coming from fluorescent materials excited by other forms of radiation.

Henri Becquerel set up experiments in which pieces of fluorescent material were placed on a photographic plate wrapped in a light-proof enclosure. These were then placed in the sunlight to stimulate fluorescence in the material after which the photographic plates were developed to look for signs of a penetrating radiation.

One of the fluorescent materials that Becquerel was using was a compound of uranium.

A period of bad weather (when he could not place the materials in direct sunlight) caused Becquerel to delay some of his experiments. He stored his uranium in contact with the photographic plates for several days out of the sunlight. When he developed the plates he observed darkening and an image of a metal cross which he had placed between the uranium and the photographic plate. The uranium was apparently producing a penetrating radiation without being exposed to any other form of radiation such as sunlight, demonstrating that fluorescence or phosphorescence was apparently not required to produce the radiation. A photographic print showing this effect is dated March 2, 1896.

Professor Becquerel continued his experiments during the month of March and determined that the penetrating radiation came from all uranium compounds, whether they were fluorescent or not.

This characteristic of certain materials, such as uranium, to spontaneously emit a radiation which penetrates like x-radiation will later become known as radioactivity.


In the Nov. 1, 1895 edition of The X-ray Century we examined the history of gas discharge tubes.

In the Nov. 8, 1895 edition of The X-ray Century we were there when Prof. Roentgen discovered a new kind of ray.

In the Dec. 1, 1895 edition of The X-ray Century we looked at the investigation which led Dr. Roentgen to write this paper.

In the Jan. 1, 1896 edition of The X-ray Century we read Prof. Roentgen's first paper describing the new kind of ray.

In the Feb. 1, 1896 edition of The X-ray Century we watched the word spread around the world.

In the March 1, 1896 edition of The X-ray Century we saw the first uses of x-rays for diagnostic purposes in several different countries.


The next edition of The X-ray Century will be published on May 1.


You are visitor number to this web site since January 26, 1996.

Webmaster: medjep@emory.edu