thermal electron emission)
71Atom — The atom is the smallest unit of an element that retains the chemical properties of that element. An atom has an electron cloud consisting of negatively charged electrons surrounding a dense nucleus. The nucleus contains positively charged… …
72Caesium — xenon ← caesium → barium Rb ↑ Cs ↓ Fr …
73Light-emitting diode — LED redirects here. For other uses, see LED (disambiguation). Light emitting diode Red, pure green and blue LEDs of the 5mm diffused type Type Passive, optoelectronic Working principle Electr …
74Spectroscopy — Analysis of white light by dispersing it with a prism is example of spectroscopy. Spectroscopy ( …
75List of materials analysis methods — List of materials analysis methods: Contents: Top · 0–9 · A B C D E F G H I J K L M N O P Q R S T U V W X Y Z μSR see Muon spin spectroscopy …
76Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… …
77Fluorescent lamp — A fluorescent lamp or fluorescent tube is a gas discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light.Unlike… …
78petroleum refining — Introduction conversion of crude oil into useful products. History Distillation of kerosene and naphtha The refining of crude petroleum owes its origin to the successful drilling of the first oil well in Titusville, Pa., in 1859. Prior to… …
79Physical Sciences — ▪ 2009 Introduction Scientists discovered a new family of superconducting materials and obtained unique images of individual hydrogen atoms and of a multiple exoplanet system. Europe completed the Large Hadron Collider, and China and India took… …
80Population inversion — In physics, specifically statistical mechanics, a population inversion occurs when a system (such as a group of atoms or molecules) exists in state with more members in an excited state than in lower energy states. The concept is of fundamental… …
