Wilhelm Ludwig Franz Hallwachs (Darmstadt , July 9 of 1859 - Dresden , June 20 from 1922) was a German physicist. He studied physics at the Universities of Berlin and Strasbourg, where he honored under the guidance of AA Kundt.

Biography

Hallwachs was an assistant at the University of Würzburg from 1884 to 1886. Soon after, he went to Leipzig, from 1886 to 1888, to work with GH Wiedemann, having married his daughter. He was professor of electrical engineering at the University of Dresden in 1893, moving later to physics in 1900. Hallwachs was a great builder of scientific instruments. Among the many devices he invented, are in the electrometer quadrant and a double refractometer great precision.

Hallwachs was assistant of Heinrich Hertz, in 1886, before the photoelectric effect was discovered. Hallwachs with Hertz, in 1887, carried on the investigations of electromagnetic waves. In 1888 he formulated the hypothesis that a conductive plate on which to focus ultraviolet light carries a positive charge because the electrons are gouged out. Interestingly this happened with more intensity in selenium. The phenomenon was seen in the same year by A. Righi. The phenomenon was called 'Hallwachs-Effekt', now called the photoelectric effect

Photoelectric effect

In the photoelectric effect, electrons are emitted from matter as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength, such as visible or ultraviolet light. Electrons emitted in this manner may be referred to as photoelectrons...

. The investigation of the photoelectric effect laid the foundation for the development of the photoelectric cell, photo electricity and Albert Einstein's quantum light hypothesis.