Nuclear energy

Discovery of Radioactivity

Discovery of radioactivity

In 1896, the French physicist Antoine Henri Becquerel discovers that certain substances produced penetrating radiation of unknown origin. This fact was named as we know it today: radioactivity.

Two years before, in 1895, the German physicist Wilhelm Conrad Röntgen discovered X-rays. He worked with Hittorff-Crookes tubes and the Ruhmkorff coil to investigate the violet fluorescence produced by cathode rays.

In Paris, the French Academy commissioned Henri Becquerel an investigation. They wanted him to investigate whether certain mineral salts could produce the discovery of the X-rays.

The Discovery of Natural Radioactivity

Becquerel was working on cathode ray fluorescence. By chance, he left some uranium salts next to photographic plates. Later, the plates appeared exposed despite being protected from sunlight.

He discovered that uranium salts emit penetrating radiation that can mark a photographic plate. Further studies made it clear that this radiation was something new and not X-ray radiation.

To test his idea, Becquerel wrapped photographic plates in a black paper so that sunlight could not reach them. He then placed the crystals of uranium salt on top of the clad plate.

When he developed the plates, he saw an outline of the crystals. He also placed objects such as coins or cut out metal shapes between the crystals and the slab. In the end, he found that he could produce outlines of those shapes on the plates.

Becquerel is considered the "father of nuclear energy.”

It is when he discovers radioactivity. Thanks to this work on radioactivity, Becquerel shared the 1903 Nobel Prize in Physics.

Who Discovered Polonium and Radium?

At the same time, the French couple formed by Pierre and Marie Curie found other radioactive substances. The Curies discovered two new elements: polonium and radium.

The spouses Pierre and Marie Curie deduced the existence of another element with higher activity than uranium. In honor of his homeland, they named it polonium. The second element they discovered was the radius.

The radiation emitted by radio was intricate. By applying a magnetic field to it, part of it deviated from its path, and another part was not.

Who Discovered the Three Types of Radiation?

Later, Ernest Rutherford and Soddy showed that uranium and other heavy elements emit three types of radiation:

The first two are made up of charged particles. The alpha particles were nuclei of helium atoms, and the beta particles were electrons. The gamma radiation was like waves in nature.

Gamma Rays

Paul Villard discovered γ rays in 1900 while he was studying radiation emitted by radio. Villard knew that this radiation was more potent than, at one time, previous types (beta rays and alpha rays).

Ernest Rutherford recognized Villard's theories as different types of rays. He named them "gamma rays" by analogy with alpha and β rays that he had discerned into 1899.

The Discovery of Artificial Radioactivity

Artificial radioactivity is also known as induced radioactivity. It is the radioactivity of substances caused by man in various activities such as:

  • Medicine.

  • Industry.

  • Mining.

  • Weapons.

  • Nuclear power plants.

When neutrons or protons irradiate stable nuclei, they can turn into radioactive. These nuclei keep on emitting radiation for a long time after the irradiation ends. The radioactivity induced by a neutron is very strong.

Who Discovered Artificial Radioactivity?

The couple formed by Frédèric Joliot and Irene Curie were the discoverers of artificial radioactivity.

The couple worked out that radioactivity could be human-made. By bombarding some chemical elements with alpha particles, it was possible to get radioactive elements.

They observed that the bombarded substances emitted radiation after removing the radioactive body emitting the bombardment particles.


Published: September 29, 2020
Last review: October 3, 2020