(adiabatic)
121Entropy — This article is about entropy in thermodynamics. For entropy in information theory, see Entropy (information theory). For a comparison of entropy in information theory with entropy in thermodynamics, see Entropy in thermodynamics and information… …
122Born-Oppenheimer approximation — In quantum chemistry, the computation of the energy and wavefunction of an average size molecule is a formidable task that is alleviated by the Born Oppenheimer (BO) approximation. For instance the benzene molecule consists of 12 nuclei and 42… …
123Speed of sound — Sound is a vibration that travels through an elastic medium as a wave. The speed of sound describes how much distance such a wave travels in a certain amount of time. In SI Units with dry air at 20 °C (68 °F), the speed of sound is 343 m/s. This… …
124Precipitation (meteorology) — Long term mean precipitation by month In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under… …
125Perturbation theory (quantum mechanics) — In quantum mechanics, perturbation theory is a set of approximation schemes directly related to mathematical perturbation for describing a complicated quantum system in terms of a simpler one. The idea is to start with a simple system for which a …
126Isentropic process — In thermodynamics, an isentropic process ( iso = equal (Greek); entropy = disorder ) is one during which the entropy of the system remains constant. [Van Wylen, G.J. and Sonntag, R.E., Fundamentals of Classical Thermodynamics , Section 7.4]… …
127Potential temperature — The potential temperature of a parcel of fluid at pressure P is the temperature that the parcel would acquire if adiabatically brought to a standard reference pressure P {0}, usually 1000 millibars. The potential temperature is denoted heta and,… …
128Polytropic process — A polytropic process is a thermodynamic process that obeys the relation::P V^n = C,where P is pressure, V is volume, n is any real number (the polytropic index), and C is a constant. This equation can be used to accurately characterize processes… …
