Jean Perrin's Important Contributions To The Development Of Physics At The Turn Of The 19～(th) Century To The 20～(th) Century

In this thesis, the contributions of Jean Baptiste Perrin (1870-1942), which were related with science, were reviewed and studied. Perrin was a professor in the Sorbonne in France and won the Nobel Prize in physics in 1926.The thesis consists of six sections.In the first section, the educational background when Perrin studied at the Ecole normale sup erieure were reviewed, as well as the scientific circumstances, emphasized at the controversy between the Atomism and Energetics. Perrin' teacher, Brillouin, was also introduced to the readers.In the second section, what Perrin had done in the initial period of his scientific career was treated. It was composed of four parts, namely Perrin's researches on cathode rays, X rays and the imagination on the structure of atoms as well as his career as a teacher on physical chemistry. At the end of the 19^th century, the cathode rays were discovered. The discussion on the properties of the cathode rays made the physical scientists divide into two groups. By and large, the physicists in Germany maintained the idea that cathode rays is the fluctuation of ether, while the physicists in B.E. and France bored the note that cathode rays was made up of particles. Then, Perrin designed a experiment to support the latter and found that the cathode rays was negative charged. In 1897, J.J.Thomson developed Perrin's experiment and surveyed the ratio of e/m , then, the dispute was settled. At the same time, Perrin carried out the research on X rays and obtained some significant results. Perrin also suspected a model of the substructure of atoms. In 1898, the Sorbonne authorized him to teach the new subject, physical chemistry. After his visit to the physical chemistry labs abroad, he established his own lab and wrote out his famous textbook, Les Principes. Because of his success in teaching, the Sorbonne created a chair for him.In the third section, Perrin's studies on the Brownian movement was the emphases. When he gave a class on physical chemistry in the Sorbonne, he began to detect the movement of colloids, and was very interested in the Brownian movement. At that time, Einstein had already proposed to use the kinetic theory to explain the Brownianmovement and waited for some scientists to sustain his theory by experimental results. In 1908, Perrin performed a series of experiments. By the means of various methods, Perrin obtained the coincide Avogadro's constant. So that, Einstein's theory was verified and it was the first time that the molecular hypothesis was directly proved to be reality. In 1913, Perrin's Atoms was published, it received passionate applause and had been translated into many foreign languages.In the fourth section, we can see that Perrin's work was interrupted by the War I . After the war, Perrin' major work was on fluorescence. Perrin's work in this period was just generally narrated.The fifth section was devoted to reveal Perrin's contribution to the scientific revival in France and its popularization in the youth. The Palace of Discovery and CNRS, were built up thanks for Perrin.In the last section, some results were obtained by analysis. Perrin's success was not just accidental, the educational background, his special method in research, the influence by his friends and the country's conditions in the Third Franc Republic as well, had played positive and active role in it.