A quantum mechanical effect in which particles have a finite probability of crossing an energy barrier, such as the energy needed to break a bond with another particle, even though the particle’s energy is less than the energy barrier. Quantum tunneling has no counterpart in classical mechanics, in which a particle can never cross an energy barrier with a higher energy level than the particle has. The emission of alpha rays in radioactive decay is a case of quantum tunneling; though the alpha particles are strongly bound to the nucleus and don’t have as much energy as the bond does, they still have a finite probability of escaping the nucleus. The design of transistors and many diodes makes use of this effect. See also radioactivity.
[kvahnts] /kvɑnts/ noun 1. Johann Joachim [yoh-hahn yoh-ah-khim] /ˈyoʊ hɑn ˈyoʊ ɑ xɪm/ (Show IPA), 1697–1773, German flutist and composer: teacher of Frederick the Great.
[chwahn-joh] /ˈtʃwɑnˈdʒoʊ/ noun, Pinyin. 1. a seaport in SE Fujian province, in SE China, on Taiwan Strait.
[kwah-oh] /ˈkwɑ oʊ/ noun 1. a male day name for Thursday. See under . noun 1. (formerly, especially in creole-speaking cultures) a name given at birth to a black child, in accordance with African customs, indicating the child’s sex and the day of the week on which he or she was born, as the male […]
Quaoar (kwä’ə-wär’) A Kuiper belt object that, with a diameter of about 1,288 km (800 mi), is the largest such object so far discovered. Quaoar is approximately the size of Charon, Pluto’s moon, and has a nearly circular orbit at a distance of some 1.6 billion km (1 billion mi) beyond that of Pluto.