This is the principle of operation of a pith-ball electroscope. The quartz fiber dosimeter is a rugged form of a device called a Lauritsen electroscope. Julian is amazed by a television-like device, called the electroscope. Abraham Bennet, the inventor of the gold-leaf electroscope and developer of an improved magnetometer. Hallwachs connected a zinc plate to an electroscope. The catcher was attached to an electroscope to measure its charge. This will discharge a negatively charged electroscope and further charge a positive electroscope. The electroscope was the first electrical measuring instrument. The Braun electroscope replaced the gold-leaf electroscope for more accurate measurements. A type of electroscope is also used in the quartz fiber radiation dosimeter. In 1903, Henri Becquerel used the Hurmuzescu electroscope in Nobel Prize-awarded radioactivity research. An electroscope is an important tool in illustrating the photoelectric effect. Often the electroscope will have a pair of suspended pith balls. The gold-leaf electroscope was one of the instruments used to indicate electric charge. In the same year, he also invented an electroscope.