Seminar "The photoelectric effect: Einstein explanation and its consequences"

Talk for a general audience

101 years ago, Albert Einstein was awarded with the Nobel price of Physics for the explanation of the photoelectric effect published in 1905 at the age of 26. He introduced revolutionary ideas that are in the basis of quantum physics. The talk will try to explain the contribution of Einstein and its consequences in everyday life. First, an introduction on how the situation concerning the nature of light was, before the Einstein work. Then the photoelectric effect will be described and also the explanation that he proposed postulating the concept of what we call, nowadays, photon. The photon concept was strongly rejected at the beginning but it was accepted after a time. A direct application of the photoelectric effect is the experimental technique of photoemission. This technique was strongly developed by K. Siegbahn who received a Nobel price.  At ALBA, CIRCE and Lorea are beamlines devoted to photoemission and also another one, 3Sbar, that is under design. Examples will illustrate their utility and their limitations. The seminal ideas introduced by Einstein are used today to explain how solar cells and Light Emitting Diodes (LED) work and also the mechanism of photocatalysis for water splitting. These examples will be briefly described.