the derived SI unit of frequency; the frequency of a periodic phenomenon that has a periodic time of 1 second; 1 cycle per second

Gustav (ˈɡʊstaf). 1887–1975, German atomic physicist. He provided evidence for the quantum theory by his research with Franck on the effects produced by bombarding atoms with electrons: they shared the Nobel prize for physics (1925)

Heinrich Rudolph (ˈhainrɪç ˈruːdɔlf). 1857–94, German physicist. He was the first to produce electromagnetic waves artificially