Louis de Broglie a solitary physicist and the everyday life

This article, written in memory of the late Louis de Broglie, begins with the short portrayal of a man of many secrets whose precise knowledge of a number of technical subjects was paralleled by a vast learning which ranged from scientific to literary and historical fields. Most of his life however was devoted to a single problem, namely the coexistence of waves and particles. The greater part of the article then deals with the practical applications of wave mechanics and more generally with different phenomena of technical processes which demonstrate under various guises the wave properties of matter